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2021-08-11x86/ELF: fix .tfloat outputJan Beulich7-6/+60
The ELF psABI-s are quite clear here: On 32-bit the data type is 12 bytes long (with 2 bytes of trailing padding), while on 64-bit it is 16 bytes long (with 6 bytes of padding). Make ieee_md_atof() capable of handling such padding, and specify the needed padding for x86 (leaving non-ELF targets alone for now). Split the existing x86 testcase.
2021-08-11x86: have non-PE/COFF BEOS be recognized as ELFJan Beulich1-0/+5
BEOS, unless explicitly requesting *-*-beospe* targets, uses standard ELF. None of the newly enabled tests in the testsuite fail for me.
2021-08-11PR28163, Segment fault in function rl78_special_relocAlan Modra1-365/+360
Relocation offset checks were completely missing in the rl78 backend, allowing a relocation to write over memory anywhere. This was true for rl78_special_reloc, a function primarily used when applying debug relocations, and in rl78_elf_relocate_section used by the linker. This patch fixes those problems by correcting inaccuracies in the relocation howtos, then uses those howtos to sanity check relocation offsets before applying relocations. In addition, the patch implements overflow checking using the howto information rather than the ad-hoc scheme implemented in relocate_section. I implemented the overflow checking in rl78_special_reloc too. * elf32-rl78.c (RL78REL, RL78_OP_REL): Add mask parameter. (rl78_elf_howto_table): Set destination masks. Correct size and bitsize of DIR32_REV. Correct complain_on_overflow for many relocs as per tests in relocate_section. Add RH_SFR. Correct bitsize for RH_SADDR. Set size to 3 and bitsize to 0 for all OP relocs. (check_overflow): New function. (rl78_special_reloc): Check that reloc address is within section. Apply relocations using reloc howto. Check for overflow. (RANGE): Delete. (rl78_elf_relocate_section): Sanity check r_offset. Perform overflow checking using reloc howto.
2021-08-11Automatic date update in version.inGDB Administrator1-1/+1
2021-08-10Ignore .debug_types when reading .debug_arangesTom Tromey2-1/+8
I noticed that the fission-reread.exp test case can cause a complaint when run with --target_board=cc-with-debug-names: warning: Section .debug_aranges in [...]/fission-reread has duplicate debug_info_offset 0x0, ignoring .debug_aranges. The bug here is that this executable has both .debug_info and .debug_types, and both have a CU at offset 0x0. This triggers the duplicate warning. Because .debug_types doesn't provide any address ranges, these CUs can be ignored. That is, this bug turns out to be another regression from the info/types merger patch. This patch fixes the problem by having this loop igore type units. fission-reread.exp is updated to test for the bug.
2021-08-10Generalize addrmap dumpingTom Tromey3-51/+46
While debugging another patch series, I wanted to dump an addrmap. I came up with this patch, which generalizes the addrmap-dumping code from psymtab.c and moves it to addrmap.c. psymtab.c is changed to use the new code.
2021-08-10gdb: iterate only on vfork parent threads in handle_vfork_child_exec_or_exitSimon Marchi1-17/+12
I spotted what I think is a buglet in proceed_after_vfork_done. After a vfork child exits or execs, we resume all the threads of the parent. To do so, we iterate on all threads using iterate_over_threads with the proceed_after_vfork_done callback. Each thread is resumed if the following condition is true: if (thread->ptid.pid () == pid && thread->state == THREAD_RUNNING && !thread->executing && !thread->stop_requested && thread->stop_signal () == GDB_SIGNAL_0) where `pid` is the pid of the vfork parent. This is not multi-target aware: since it only filters on pid, if there is an inferior with the same pid in another target, we could end up resuming a thread of that other inferior. The chances of the stars aligning for this to happen are tiny, but still. Fix that by iterating only on the vfork parent's threads, instead of on all threads. This is more efficient, as we iterate on just the required threads (inferiors have their own thread list), and we can drop the pid check. The resulting code is also more straightforward in my opinion, so it's a win-win. Change-Id: I14647da72e2bf65592e82fbe6efb77a413a4be3a
2021-08-10Updated Serbian and Russian translations for various sub-directoriesNick Clifton10-8960/+10256
2021-08-09guile: fix smob exportsGeorge Barrett2-1/+56
Before Guile v2.1 [1], calls to `scm_make_smob_type' implicitly added the created class to the exports list of (oop goops); v2.1+ does not implicitly create bindings in any modules. This means that the GDB manual subsection documenting exported types is not quite right when GDB is linked against Guile <v2.1 (types are exported from (oop goops)) instead of (gdb)) and incorrect when linked against Guile v2.1+ (types are not bound to any variables at all!). There is a range of cases in which it's necessary or convenient to be able to refer to a GDB smob type, for instance: - Pattern matching based on the type of a value. - Defining GOOPS methods handling values from GDB (GOOPS methods typically use dynamic dispatch based on the types of the arguments). - Type-checking assertions when applying some defensive programming on an interface. - Generally any other situation one might encounter in a dynamically typed language that might need some introspection. If you're more familiar with Python, it would be quite similar to being unable to refer to the classes exported from the GDB module (which is to say: not crippling for the most part, but makes certain tasks more difficult than necessary). This commit makes a small change to GDB's smob registration machinery to make sure registered smobs get exported from the current module. This will likely cause warnings to the user about conflicting exports if they load both (gdb) and (oop goops) from a GDB linked against Guile v2.0, but it shouldn't impact functionality (and seemed preferable to trying to un-export bindings from (oop goops) if v2.0 was detected). [1]: This changed with Guile commit 28d0871b553a3959a6c59e2e4caec1c1509f8595 gdb/ChangeLog: 2021-06-07 George Barrett <bob@bob131.so> * guile/scm-gsmob.c (gdbscm_make_smob_type): Export registered smob type from the current module. gdb/testsuite/ChangeLog: 2021-06-07 George Barrett <bob@bob131.so> * gdb.guile/scm-gsmob.exp (test exports): Add tests to make sure the smob types currently listed in the GDB manual get exported from the (gdb) module. Change-Id: I7dcd791276b48dfc9edb64fc71170bbb42a6f6e7
2021-08-10Automatic date update in version.inGDB Administrator1-1/+1
2021-08-09GAS: DWARF-5: Ensure that the 0'th entry in the directory table contains the ↵Nick Clifton8-18/+91
current working directory. * dwarf2dbg.c (get_directory_table_entry): Ensure that dir[0] contains current working directory. (out_dir_and_file_list): Likewise. * testsuite/gas/elf/dwarf-5-dir0.s: New test source file. * testsuite/gas/elf/dwarf-5-dir0.d: New test driver. * testsuite/gas/elf/elf.exp: Run the new test. * testsuite/gas/elf/dwarf-5-file0.d: Adjust expected output. * testsuite/gas/i386/dwarf5-line-1.d: Likewise. * testsuite/gas/i386/dwarf5-line-2.d: Likewise.
2021-08-09Automatic date update in version.inGDB Administrator1-1/+1
2021-08-08Include objfiles.h in a few .c filesTom Tromey3-0/+3
I found a few .c files that rely on objfiles.h, but that only include it indirectly, via dwarf2/read.h -> psympriv.h. If that include is removed (something my new DWARF indexer series does), then the build will break. It seemed harmless and correct to add these includes now, making the eventual series a little smaller.
2021-08-08Automatic date update in version.inGDB Administrator1-1/+1
2021-08-07PR28186, SEGV elf.c:7991:30 in _bfd_elf_fixup_group_sectionsAlan Modra1-1/+1
PR 28186 * elf.c (_bfd_elf_fixup_group_sections): Don't segfault on objcopy/strip with NULL output_section.
2021-08-07PR28176, rl78 complex reloc divide by zeroAlan Modra1-129/+154
This is a bit more than just preventing the divide by zero. Most of the patch is tidying up error reporting, so that for example, linking an object file with a reloc stack underflow produces a linker error rather than just displaying a message that might be ignored. PR 28176 * elf32-rl78.c (RL78_STACK_PUSH, RL78_STACK_POP): Delete. (rl78_stack_push, rl78_stack_pop): New inline functions. (rl78_compute_complex_reloc): Add status and error message params. Use new inline stack handling functions. Report stack overflow or underflow, and divide by zero. (rl78_special_reloc): Return status and error message from rl78_compute_complex_reloc. (rl78_elf_relocate_section): Similarly. Modernise reloc error reporting. Delete unused bfd_reloc_other case. Don't assume DIR24S_PCREL overflow is due to undefined function. (rl78_offset_for_reloc): Adjust to suit rl78_compute_complex_reloc.
2021-08-07Automatic date update in version.inGDB Administrator1-1/+1
2021-08-06[gdb/symtab] Recognize .gdb_index symbol table with empty entries as emptyTom de Vries2-20/+11
When reading a .gdb_index that contains a non-empty symbol table with only empty entries, gdb doesn't recognize it as empty. Fix this by recognizing that the constant pool is empty, and then setting the symbol table to empty. Tested on x86_64-linux. gdb/ChangeLog: 2021-08-01 Tom de Vries <tdevries@suse.de> PR symtab/28159 * dwarf2/read.c (read_gdb_index_from_buffer): Handle symbol table filled with empty entries. gdb/testsuite/ChangeLog: 2021-08-01 Tom de Vries <tdevries@suse.de> PR symtab/28159 * gdb.dwarf2/dw2-zero-range.exp: Remove kfail.
2021-08-06Unconditionally define _initialize_addrmapTom Tromey1-1/+3
The way that init.c is generated does not allow for an initialization function to be conditionally defined -- doing so will result in a link error. This patch fixes a build problem that arises from such a conditional definition. It can be reproduce with --disable-unit-tests.
2021-08-06[gdb/symtab] Fix zero address complaint for shlibTom de Vries4-8/+232
In PR28004 the following warning / Internal error is reported: ... $ gdb -q -batch \ -iex "set sysroot $(pwd -P)/repro" \ ./repro/gdb \ ./repro/core \ -ex bt ... Program terminated with signal SIGABRT, Aborted. #0 0x00007ff8fe8e5d22 in raise () from repro/usr/lib/libc.so.6 [Current thread is 1 (LWP 1762498)] #1 0x00007ff8fe8cf862 in abort () from repro/usr/lib/libc.so.6 warning: (Internal error: pc 0x7ff8feb2c21d in read in psymtab, \ but not in symtab.) warning: (Internal error: pc 0x7ff8feb2c218 in read in psymtab, \ but not in symtab.) ... #2 0x00007ff8feb2c21e in __gnu_debug::_Error_formatter::_M_error() const \ [clone .cold] (warning: (Internal error: pc 0x7ff8feb2c21d in read in \ psymtab, but not in symtab.) ) from repro/usr/lib/libstdc++.so.6 ... The warning is about the following: - in find_pc_sect_compunit_symtab we try to find the address (0x7ff8feb2c218 / 0x7ff8feb2c21d) in the symtabs. - that fails, so we try again in the partial symtabs. - we find a matching partial symtab - however, the partial symtab has a full symtab, so we should have found a matching symtab in the first step. The addresses are: ... (gdb) info sym 0x7ff8feb2c218 __gnu_debug::_Error_formatter::_M_error() const [clone .cold] in \ section .text of repro/usr/lib/libstdc++.so.6 (gdb) info sym 0x7ff8feb2c21d __gnu_debug::_Error_formatter::_M_error() const [clone .cold] + 5 in \ section .text of repro/usr/lib/libstdc++.so.6 ... which correspond to unrelocated addresses 0x9c218 and 0x9c21d: ... $ nm -C repro/usr/lib/libstdc++.so.6.0.29 | grep 000000000009c218 000000000009c218 t __gnu_debug::_Error_formatter::_M_error() const \ [clone .cold] ... which belong to function __gnu_debug::_Error_formatter::_M_error() in /build/gcc/src/gcc/libstdc++-v3/src/c++11/debug.cc. The partial symtab that is found for the addresses is instead the one for /build/gcc/src/gcc/libstdc++-v3/src/c++98/bitmap_allocator.cc, which is incorrect. This happens as follows. The bitmap_allocator.cc CU has DW_AT_ranges at .debug_rnglist offset 0x4b50: ... 00004b50 0000000000000000 0000000000000056 00004b5a 00000000000a4790 00000000000a479c 00004b64 00000000000a47a0 00000000000a47ac ... When reading the first range 0x0..0x56, it doesn't trigger the "start address of zero" complaint here: ... /* A not-uncommon case of bad debug info. Don't pollute the addrmap with bad data. */ if (range_beginning + baseaddr == 0 && !per_objfile->per_bfd->has_section_at_zero) { complaint (_(".debug_rnglists entry has start address of zero" " [in module %s]"), objfile_name (objfile)); continue; } ... because baseaddr != 0, which seems incorrect given that when loading the shared library individually in gdb (and consequently baseaddr == 0), we do see the complaint. Consequently, we run into this case in dwarf2_get_pc_bounds: ... if (low == 0 && !per_objfile->per_bfd->has_section_at_zero) return PC_BOUNDS_INVALID; ... which then results in this code in process_psymtab_comp_unit_reader being called with cu_bounds_kind == PC_BOUNDS_INVALID, which sets the set_addrmap argument to 1: ... scan_partial_symbols (first_die, &lowpc, &highpc, cu_bounds_kind <= PC_BOUNDS_INVALID, cu); ... and consequently, the CU addrmap gets build using address info from the functions. During that process, addrmap_set_empty is called with a range that includes 0x9c218 and 0x9c21d: ... (gdb) p /x start $7 = 0x9989c (gdb) p /x end_inclusive $8 = 0xb200d ... but it's called for a function at DIE 0x54153 with DW_AT_ranges at 0x40ae: ... 000040ae 00000000000b1ee0 00000000000b200e 000040b9 000000000009989c 00000000000998c4 000040c3 <End of list> ... and neither range includes 0x9c218 and 0x9c21d. This is caused by this code in partial_die_info::read: ... if (dwarf2_ranges_read (ranges_offset, &lowpc, &highpc, cu, nullptr, tag)) has_pc_info = 1; ... which pretends that the function is located at addresses 0x9989c..0xb200d, which is indeed not the case. This patch fixes the first problem encountered: fix the "start address of zero" complaint warning by removing the baseaddr part from the condition. Same for dwarf2_ranges_process. The effect is that: - the complaint is triggered, and - the warning / Internal error is no longer triggered. This does not fix the observed problem in partial_die_info::read, which is filed as PR28200. Tested on x86_64-linux. Co-Authored-By: Simon Marchi <simon.marchi@polymtl.ca> gdb/ChangeLog: 2021-07-29 Simon Marchi <simon.marchi@polymtl.ca> Tom de Vries <tdevries@suse.de> PR symtab/28004 * gdb/dwarf2/read.c (dwarf2_rnglists_process, dwarf2_ranges_process): Fix zero address complaint. * gdb/testsuite/gdb.dwarf2/dw2-zero-range-shlib.c: New test. * gdb/testsuite/gdb.dwarf2/dw2-zero-range.c: New test. * gdb/testsuite/gdb.dwarf2/dw2-zero-range.exp: New file.
2021-08-06Re: Add tests for Intel AVX512_FP16 instructionsAlan Modra1-0/+1
* testsuite/gas/i386/x86-64-avx512_fp16_pseudo_ops.d: Pass with mingw section padding.
2021-08-06chew ubsan warningAlan Modra1-2/+2
It matters not at all if pc is incremented from its initial NULL value, but avoid this silly runtime ubsan error. * doc/chew.c (perform): Avoid incrementing NULL pc.
2021-08-06bfd_reloc_offset_in_range overflowAlan Modra1-1/+1
This patch is more about the style of bounds checking we ought to use, rather than a real problem. An overflow of "octet + reloc_size" can only happen with huge sections which would certainly cause out of memory errors. * reloc.c (bfd_reloc_offset_in_range): Avoid possible overflow.
2021-08-06PR28175, Segment fault in coff-tic30.c reloc_processingAlan Modra3-9/+30
The obj_convert table shouldn't be accessed without first checking the index against the table size. PR 28175 * coff-tic30.c (reloc_processing): Sanity check reloc symbol index. * coff-z80.c (reloc_processing): Likewise. * coff-z8k.c (reloc_processing): Likewise.
2021-08-06PR28173, nds32_elf_howto_table index out of boundsAlan Modra1-30/+25
Indexing the howto table was seriously broken by a missing entry, and use of assertions about user input rather than testing the input. PR 28173 * elf32-nds32.c (nds32_elf_howto_table): Add missing empty howto. (bfd_elf32_bfd_reloc_type_table_lookup): Replace assertions with range checks. Return NULL if unsupported reloc type. Remove dead code. Take an unsigned int param. (nds32_info_to_howto_rel): Test for NULL howto or howto name return from lookup. Remove assertion. (nds32_info_to_howto): Remove unnecessary ATTRIBUTE_UNUSED. Test for NULL howto or howto name return from lookup.
2021-08-06PR28172, bfin_pcrel24_reloc heap-buffer-overflowAlan Modra1-5/+11
bfin pcrel24 relocs are weird, they apply to the reloc address minus two. That means reloc addresses of 0 and 1 are invalid. Check that, and fix other reloc range checking. PR 28172 * elf32-bfin.c (bfin_pcrel24_reloc): Correct reloc range check. (bfin_imm16_reloc, bfin_byte4_reloc, bfin_bfd_reloc): Likewise. (bfin_final_link_relocate): Likewise.
2021-08-06Automatic date update in version.inGDB Administrator1-1/+1
2021-08-05[PATCH] GDB Testsuite, update compile-cplus.expWill Schmidt1-5/+4
[PATCH] GDB Testsuite, update compile-cplus.exp Update the gdb.compile/compile-cplus.exp test to handle errors generated when passing bad arguments into the gdb-compile command. This matches changes made to gdb.compile/compile.exp in the past as part of "Migrate rest of compile commands to new options framework" e6ed716cd5514c08b9d7c469d185b1aa177dbc22
2021-08-05[gdb] Handle .TOC. sections during gdb-compile for rs6000 target.Will Schmidt1-0/+41
[gdb] Handle .TOC. sections during gdb-compile for rs6000 target. When we encounter a .TOC. symbol in the object we are loading, we need to associate this with the .toc section in order to properly resolve other symbols in the object. IF a .toc section is not found, iterate the sections until we find one with the SEC_ALLOC flag. If that also fails, fall back to using the *ABS* section, pointed to by bfd_abs_section_ptr.
2021-08-05gdb/testsuite: gdb.base/attach.exp: expose bug when testing with ↵Simon Marchi1-6/+21
native-extended-gdbserver In gdb.base/attach.exp, proc do_attach_failure_tests, we attach to a process. When then try to attach to the same process in another inferior, expecting it to fail. We then come back to the first inferior and try to kill it, to clean up the test. When using the native-extended-gdbserver board, this "kill" test passes, even though it didn't actually work: add-inferior [New inferior 2] Added inferior 2 on connection 1 (extended-remote localhost:2347) (gdb) PASS: gdb.base/attach.exp: do_attach_failure_tests: add empty inferior 2 inferior 2 [Switching to inferior 2 [<null>] (<noexec>)] (gdb) PASS: gdb.base/attach.exp: do_attach_failure_tests: switch to inferior 2 attach 817032 Attaching to process 817032 Attaching to process 817032 failed (gdb) PASS: gdb.base/attach.exp: do_attach_failure_tests: fail to attach again inferior 1 [Switching to inferior 1 [process 817032] (/home/simark/build/binutils-gdb/gdb/testsuite/outputs/gdb.base/attach/attach)] [Switching to thread 1.1 (Thread 817032.817032)] #0 main () at /home/simark/src/binutils-gdb/gdb/testsuite/gdb.base/attach.c:19 19 while (! should_exit) (gdb) PASS: gdb.base/attach.exp: do_attach_failure_tests: switch to inferior 1 kill Kill the program being debugged? (y or n) y Remote connection closed <==== That's unexpected (gdb) PASS: gdb.base/attach.exp: do_attach_failure_tests: exit after attach failures When the second attach fails, gdbserver seems to break the connection (it hangs up on the existing remote target) and start listening again for incoming connections. This is documented in PR 19558 [1]. Make the expected output regexp for the kill command tighter (it currently accepts anything). Use "set confirm off" so we don't have to deal with the confirmation. And to be really sure the extended-remote target still works, try to run the inferior again after killing. The now tests are kfail'ed when the target is gdbserver. [1] https://sourceware.org/bugzilla/show_bug.cgi?id=19558 gdb/testsuite/ChangeLog: * gdb.base/attach.exp (do_attach_failure_tests): Make kill regexp tighter, run inferior after killing it. Kfail when target is gdbserver. Change-Id: I99c5cd3968ce2ec962ace35b016f842a243b7a0d
2021-08-05gdb/testsuite: gdb.base/attach.exp: fix support check in ↵Simon Marchi1-7/+12
test_command_line_attach_run When running this test with the native-extended-gdbserver, we get: main () at /home/simark/src/binutils-gdb/gdb/testsuite/gdb.base/attach.c:19 19 while (! should_exit) The program being debugged has been started already. Start it from the beginning? (y or n) PASS: gdb.base/attach.exp: cmdline attach run: run to prompt y Don't know how to run. Try "help target". (gdb) FAIL: gdb.base/attach.exp: cmdline attach run: run to main This test tests using both "-p <pid>" and "-ex start" on the command line, making sure that we first attach and then run. Normally, after that "y", we should see the program running again. However, a particuliarity of the native-extended-gdbserver is that it uses "set auto-connect-native-target off" on the command line. The full GDB command line is: ./gdb -nw -nx -data-directory /home/simark/build/binutils-gdb/gdb/testsuite/../data-directory \ -iex set height 0 -iex set width 0 -ex set auto-connect-native-target off \ -ex set sysroot -quiet -iex set height 0 -iex set width 0 --pid=536609 -ex start The attach succeeds. I guess it is done before "set auto-connect-native-target off", or it somehow bypasses it. When the "start" is executed, the native target is unpushed, while killing the existing process, but not re-pushed, due to "set auto-connect-native-target off". So we get that "Don't know how to run" message. Really, I think it's a case of the test doing things incompatible with the board, I think it should just be skipped. And as we can see with the current code, there were some attempts at doing this, just using the wrong checks: - isnative: this is a dejagnu proc which checks if the target board has the same triplet as the build machine. In the case of native-extended-gdbserver, it does. - is_remote target: this checks whether the target board is remote, as in executing on a different machin. native-extended-gdbserver is not remote. Since the --pid option specifically attaches to a process using the native target, change the test to use gdb_is_target_native instead. gdb/testsuite/ChangeLog: * gdb.base/attach.exp (test_command_line_attach_run): Use gdb_is_target_native to check if test is supported. Change-Id: I762e127f39623889999dc9ed2185540a0951bfb0
2021-08-05gdb: target_waitstatus_to_string: print extra info for FORKED, VFORKED, EXECDSimon Marchi1-3/+22
Print the extra information contained in target_waitstatus for these events. For TARGET_WAITKIND_{FORKED,VFORKED}, the extra information is contained in related_pid, and is the ptid of the new process. For TARGET_WAITKIND_EXECD, it,s the exec'd path name in execd_pathname. Print it using the same format used for TARGET_WAITKIND_STOPPED and others. Here are sample outputs for all three events: [infrun] print_target_wait_results: target_wait (-1.0.0 [process -1], status) = [infrun] print_target_wait_results: 726890.726890.0 [process 726890], [infrun] print_target_wait_results: status->kind = vforked, related_pid = 726894.726894.0 [infrun] print_target_wait_results: target_wait (-1.0.0 [process -1], status) = [infrun] print_target_wait_results: 727045.727045.0 [process 727045], [infrun] print_target_wait_results: status->kind = forked, related_pid = 727049.727049.0 [infrun] print_target_wait_results: target_wait (-1.0.0 [process -1], status) = [infrun] print_target_wait_results: 727119.727119.0 [process 727119], [infrun] print_target_wait_results: status->kind = execd, execd_pathname = /usr/bin/ls Change-Id: I4416a74e3bf792a625a68bf26c51689e170f2184
2021-08-05gdb: use ptid_t::to_string in print_target_wait_resultsSimon Marchi1-8/+4
The ptid_t::to_string method was introduced recently, to format a ptid_t for debug purposes. It formats the ptid exactly as is done in print_target_wait_results, so make print_target_wait_results use it. Change-Id: I0a81c8040d3e1858fb304cb28366b34d94eefe4d
2021-08-05Add as_lval argument to expression evaluatorZoran Zaric5-30/+38
There are cases where the result of the expression evaluation is expected to be in a form of a value and not location description. One place that has this requirement is dwarf_entry_parameter_to_value function, but more are expected in the future. Until now, this requirement was fulfilled by extending the evaluated expression with a DW_OP_stack_value operation at the end. New implementation, introduces a new evaluation argument instead. * dwarf2/expr.c (dwarf_expr_context::fetch_result): Add as_lval argument. (dwarf_expr_context::eval_exp): Add as_lval argument. * dwarf2/expr.h (struct dwarf_expr_context): Add as_lval argument to fetch_result and eval_exp methods. * dwarf2/frame.c (execute_stack_op): Add as_lval argument. * dwarf2/loc.c (dwarf_entry_parameter_to_value): Remove DWARF expression extension. (dwarf2_evaluate_loc_desc_full): Add as_lval argument support. (dwarf2_evaluate_loc_desc): Add as_lval argument support. (dwarf2_locexpr_baton_eval): Add as_lval argument support.
2021-08-05Simplify dwarf_expr_context class interfaceZoran Zaric4-232/+237
Idea of this patch is to get a clean and simple public interface for the dwarf_expr_context class, looking like: - constructor, - destructor, - push_address method and - evaluate method. Where constructor should only ever require a target architecture information. This information is held in per object file (dwarf2_per_objfile) structure, so it makes sense to keep that structure as a constructor argument. It also makes sense to get the address size from that structure, but unfortunately that interface doesn't exist at the moment, so the dwarf_expr_context class user needs to provide that information. The push_address method is used to push a CORE_ADDR as a value on top of the DWARF stack before the evaluation. This method can be later changed to push any struct value object on the stack. The evaluate method is the method that evaluates a DWARF expression and provides the evaluation result, in a form of a single struct value object that describes a location. To do this, the method requires a context of the evaluation, as well as expected result type information. If the type information is not provided, the DWARF generic type will be used instead. To avoid storing the gdbarch information in the evaluator object, that information is now always acquired from the per_objfile object. All data members are now private and only visible to the evaluator class, so a m_ prefix was added to all of their names to reflect that. To make this distinction clear, they are also accessed through objects this pointer, wherever that was not the case before. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::dwarf_expr_context): Add address size argument. (dwarf_expr_context::read_mem): Change to use property_addr_info structure. (dwarf_expr_context::evaluate): New function. (dwarf_expr_context::execute_stack_op): Change to use property_addr_info structure. * dwarf2/expr.h (struct dwarf_expr_context): New evaluate declaration. Change eval and fetch_result method to private. (dwarf_expr_context::gdbarch): Remove member. (dwarf_expr_context::stack): Make private and add m_ prefix. (dwarf_expr_context::addr_size): Make private and add m_ prefix. (dwarf_expr_context::recursion_depth): Make private and add m_ prefix. (dwarf_expr_context::max_recursion_depth): Make private and add m_ prefix. (dwarf_expr_context::len): Make private and add m_ prefix. (dwarf_expr_context::data): Make private and add m_ prefix. (dwarf_expr_context::initialized): Make private and add m_ prefix. (dwarf_expr_context::pieces): Make private and add m_ prefix. (dwarf_expr_context::per_objfile): Make private and add m_ prefix. (dwarf_expr_context::frame): Make private and add m_ prefix. (dwarf_expr_context::per_cu): Make private and add m_ prefix. (dwarf_expr_context::addr_info): Make private and add m_ prefix. * dwarf2/frame.c (execute_stack_op): Change to call evaluate method. * dwarf2/loc.c (dwarf2_evaluate_loc_desc_full): Change to call evaluate method. (dwarf2_locexpr_baton_eval): Change to call evaluate method.
2021-08-05Make DWARF evaluator return a single struct valueZoran Zaric5-198/+203
The patch is addressing the issue of class users writing and reading the internal data of the dwarf_expr_context class. At this point, all conditions are met for the DWARF evaluator to return an evaluation result in a form of a single struct value object. gdb/ChangeLog: * dwarf2/expr.c (pieced_value_funcs): Chenge to static function. (allocate_piece_closure): Change to static function. (dwarf_expr_context::fetch_result): New function. * dwarf2/expr.h (struct piece_closure): Remove declaration. (struct dwarf_expr_context): fetch_result new declaration. fetch, fetch_address and fetch_in_stack_memory members move to private. (allocate_piece_closure): Remove. * dwarf2/frame.c (execute_stack_op): Change to use fetch_result. * dwarf2/loc.c (dwarf2_evaluate_loc_desc_full): Change to use fetch_result. (dwarf2_locexpr_baton_eval): Change to use fetch_result. * dwarf2/loc.h (invalid_synthetic_pointer): Expose function.
2021-08-05Make value_copy also copy the stack data memberZoran Zaric1-0/+2
Fixing a bug where the value_copy function did not copy the stack data and initialized members of the struct value. This is needed for the next patch where the DWARF expression evaluator is changed to return a single struct value object. * value.c (value_copy): Change to also copy the stack data and initialized members.
2021-08-05Move piece_closure and its support to expr.cZoran Zaric4-599/+595
Following 5 patches series is trying to clean up the interface of the DWARF expression evaluator class (dwarf_expr_context). After merging all expression evaluators into one class, the next logical step is to make a clean user interface for that class. To do that, we first need to address the issue of class users writing and reading the internal data of the class directly. Fixing the case of writing is simple, it makes sense for an evaluator instance to be per architecture basis. Currently, the best separation seems to be per object file, so having that data (dwarf2_per_objfile) as a constructor argument makes sense. It also makes sense to get the address size from that object file, but unfortunately that interface does not exist at the moment. Luckily, address size information is already available to the users through other means. As a result, the address size also needs to be a class constructor argument, at least until a better interface for acquiring that information from an object file is implemented. The rest of the user written data comes down to a context of an evaluated expression (compilation unit context, frame context and passed in buffer context) and a source type information that a result of evaluating expression is representing. So, it makes sense for all of these to be arguments of an evaluation method. To address the problem of reading the dwarf_expr_context class internal data, we first need to understand why it is implemented that way? This is actualy a question of which existing class can be used to represent both values and a location descriptions and why it is not used currently? The answer is in a struct value class/structure, but the problem is that before the evaluators were merged, only one evaluator had an infrastructure to resolve composite and implicit pointer location descriptions. After the merge, we are now able to use the struct value to represent any result of the expression evaluation. It also makes sense to move all infrastructure for those location descriptions to the expr.c file considering that that is the only place using that infrastructure. What we are left with in the end is a clean public interface of the dwarf_expr_context class containing: - constructor, - destructor, - push_address method and - eval_exp method. The idea with this particular patch is to move piece_closure structure and the interface that handles it (lval_funcs) to expr.c file. While implicit pointer location descriptions are still not useful in the CFI context (of the AMD's DWARF standard extensions), the composite location descriptions are certainly necessary to describe a results of specific compiler optimizations. Considering that a piece_closure structure is used to represent both, there was no benefit in splitting them. gdb/ChangeLog: * dwarf2/expr.c (struct piece_closure): Add from loc.c. (allocate_piece_closure): Add from loc.c. (bits_to_bytes): Add from loc.c. (rw_pieced_value): Add from loc.c. (read_pieced_value): Add from loc.c. (write_pieced_value): Add from loc.c. (check_pieced_synthetic_pointer): Add from loc.c. (indirect_pieced_value): Add from loc.c. (coerce_pieced_ref): Add from loc.c. (copy_pieced_value_closure): Add from loc.c. (free_pieced_value_closure): Add from loc.c. (sect_variable_value): Add from loc.c. * dwarf2/loc.c (sect_variable_value): Move to expr.c. (struct piece_closure): Move to expr.c. (allocate_piece_closure): Move to expr.c. (bits_to_bytes): Move to expr.c. (rw_pieced_value): Move to expr.c. (read_pieced_value): Move to expr.c. (write_pieced_value): Move to expr.c. (check_pieced_synthetic_pointer): Move to expr.c. (indirect_pieced_value): Move to expr.c. (coerce_pieced_ref): Move to expr.c. (copy_pieced_value_closure): Move to expr.c. (free_pieced_value_closure): Move to expr.c.
2021-08-05Merge evaluate_for_locexpr_baton evaluatorZoran Zaric3-55/+28
The evaluate_for_locexpr_baton is the last derived class from the dwarf_expr_context class. It's purpose is to support the passed in buffer functionality. Although, it is not really necessary to merge this class with it's base class, doing that simplifies new expression evaluator design. Considering that this functionality is going around the DWARF standard, it is also reasonable to expect that with a new evaluator design and extending the push object address functionality to accept any location description, there will be no need to support passed in buffers. Alternatively, it would also makes sense to abstract the interaction between the evaluator and a given resource in the near future. The passed in buffer would then be a specialization of that abstraction. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::read_mem): Merge with evaluate_for_locexpr_baton implementation. * dwarf2/loc.c (class evaluate_for_locexpr_baton): Remove class. (evaluate_for_locexpr_baton::read_mem): Move to dwarf_expr_context. (dwarf2_locexpr_baton_eval): Instantiate dwarf_expr_context instead of evaluate_for_locexpr_baton class.
2021-08-05Remove empty frame and full evaluatorsZoran Zaric2-29/+5
There are no virtual methods that require different specialization in dwarf_expr_context class. This means that derived classes dwarf_expr_executor and dwarf_evaluate_loc_desc are not needed any more. As a result of this, the evaluate_for_locexpr_baton class base class is now the dwarf_expr_context class. There might be a need for a better class hierarchy when we know more about the direction of the future DWARF versions and gdb extensions, but that is out of the scope of this patch series. gdb/ChangeLog: * dwarf2/frame.c (class dwarf_expr_executor): Remove class. (execute_stack_op): Instantiate dwarf_expr_context instead of dwarf_evaluate_loc_desc class. * dwarf2/loc.c (class dwarf_evaluate_loc_desc): Remove class. (dwarf2_evaluate_loc_desc_full): Instantiate dwarf_expr_context instead of dwarf_evaluate_loc_desc class. (struct evaluate_for_locexpr_baton): Derive from dwarf_expr_context.
2021-08-05Inline get_reg_value method of dwarf_expr_contextZoran Zaric2-23/+7
The get_reg_value method is a small function that is only called once, so it can be inlined to simplify the dwarf_expr_context class. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::get_reg_value): Remove method. (dwarf_expr_context::execute_stack_op): Inline get_reg_value method. * dwarf2/expr.h (dwarf_expr_context::get_reg_value): Remove method.
2021-08-05Move push_dwarf_reg_entry_value to expr.cZoran Zaric5-83/+72
Following the idea of merging the evaluators, the push_dwarf_reg_entry_value method can be moved from dwarf_expr_executor and dwarf_evaluate_loc_desc classes to their base class dwarf_expr_context. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::push_dwarf_reg_entry_value): Move from dwarf_evaluate_loc_desc. * dwarf2/frame.c (dwarf_expr_executor::push_dwarf_reg_entry_value): Remove method. * dwarf2/loc.c (dwarf_expr_reg_to_entry_parameter): Expose function. (dwarf_evaluate_loc_desc::push_dwarf_reg_entry_value): Move to dwarf_expr_context. * dwarf2/loc.h (dwarf_expr_reg_to_entry_parameter): Expose function.
2021-08-05Move read_mem to dwarf_expr_contextZoran Zaric4-13/+10
Following the idea of merging the evaluators, the read_mem method can be moved from dwarf_expr_executor and dwarf_evaluate_loc_desc classes to their base class dwarf_expr_context. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::read_mem): Move from dwarf_evaluate_loc_desc. * dwarf2/frame.c (dwarf_expr_executor::read_mem): Remove method. * dwarf2/loc.c (dwarf_evaluate_loc_desc::read_mem): Move to dwarf_expr_context.
2021-08-05Move get_object_address to dwarf_expr_contextZoran Zaric3-18/+9
Following the idea of merging the evaluators, the get_object_address and can be moved from dwarf_expr_executor and dwarf_evaluate_loc_desc classes to their base class dwarf_expr_context. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::get_object_address): Move from dwarf_evaluate_loc_desc. (class dwarf_expr_context): Add object address member to dwarf_expr_context. * dwarf2/expr.h (dwarf_expr_context::get_frame_pc): Remove method. * dwarf2/frame.c (dwarf_expr_executor::get_object_address): Remove method. * dwarf2/loc.c (dwarf_evaluate_loc_desc::get_object_address): move to dwarf_expr_context. (class dwarf_evaluate_loc_desc): Move object address member to dwarf_expr_context.
2021-08-05Move dwarf_call to dwarf_expr_contextZoran Zaric4-70/+33
Following the idea of merging the evaluators, the dwarf_call and get_frame_pc method can be moved from dwarf_expr_executor and dwarf_evaluate_loc_desc classes to their base class dwarf_expr_context. Once this is done, the get_frame_pc can be replace with lambda function. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::dwarf_call): Move from dwarf_evaluate_loc_desc. (dwarf_expr_context::get_frame_pc): Replace with lambda. * dwarf2/expr.h (dwarf_expr_context::get_frame_pc): Remove method. * dwarf2/frame.c (dwarf_expr_executor::dwarf_call): Remove method. (dwarf_expr_executor::get_frame_pc): Remove method. * dwarf2/loc.c (dwarf_evaluate_loc_desc::get_frame_pc): Remove method. (dwarf_evaluate_loc_desc::dwarf_call): Move to dwarf_expr_context. (per_cu_dwarf_call): Inline function.
2021-08-05Move compilation unit info to dwarf_expr_contextZoran Zaric5-82/+75
This patch moves the compilation unit context information and support from dwarf_expr_executor and dwarf_evaluate_loc_desc to dwarf_expr_context evaluator. The idea is to report an error when a given operation requires a compilation unit information to be resolved, which is not available. With this change, it also makes sense to always acquire ref_addr_size information from the compilation unit context, considering that all DWARF operations that refer to that information require a compilation unit context to be present during their evaluation. gdb/ChangeLog: * dwarf2/expr.c (ensure_have_per_cu): New function. (dwarf_expr_context::dwarf_expr_context): Add compilation unit context information. (dwarf_expr_context::get_base_type): Move from dwarf_evaluate_loc_desc. (dwarf_expr_context::get_addr_index): Remove method. (dwarf_expr_context::dwarf_variable_value): Remove method. (dwarf_expr_context::execute_stack_op): Call compilation unit context info check. Inline get_addr_index and dwarf_variable_value methods. * dwarf2/expr.h (struct dwarf_expr_context): Add compilation context info. (dwarf_expr_context::get_addr_index): Remove method. (dwarf_expr_context::dwarf_variable_value): Remove method. (dwarf_expr_context::ref_addr_size): Remove member. * dwarf2/frame.c (dwarf_expr_executor::get_addr_index): Remove method. (dwarf_expr_executor::dwarf_variable_value): Remove method. * dwarf2/loc.c (sect_variable_value): Expose function. (dwarf_evaluate_loc_desc::get_addr_index): Remove method. (dwarf_evaluate_loc_desc::dwarf_variable_value): Remove method. (class dwarf_evaluate_loc_desc): Move compilation unit context information to dwarf_expr_context class. * dwarf2/loc.h (sect_variable_value): Expose function.
2021-08-05Remove get_frame_cfa from dwarf_expr_contextZoran Zaric4-17/+4
Following the idea of merging the evaluators, the get_frame_cfa method can be moved from dwarf_expr_executor and dwarf_evaluate_loc_desc classes to their base class dwarf_expr_context. Once this is done, it becomes apparent that the method is only called once and it can be inlined. It is also necessary to check if the frame context information was provided before the DW_OP_call_frame_cfa operation is executed. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::get_frame_cfa): Remove method. (dwarf_expr_context::execute_stack_op): Call frame context info check for DW_OP_call_frame_cfa. Remove use of get_frame_cfa. * dwarf2/expr.h (dwarf_expr_context::get_frame_cfa): Remove method. * dwarf2/frame.c (dwarf_expr_context::get_frame_cfa): Remove method. * dwarf2/loc.c (dwarf_expr_context::get_frame_cfa): Remove method.
2021-08-05Move frame context info to dwarf_expr_contextZoran Zaric4-105/+91
Following 15 patches in this patch series is cleaning up the design of the DWARF expression evaluator (dwarf_expr_context) to make future extensions of that evaluator easier and cleaner to implement. There are three subclasses of the dwarf_expr_context class (dwarf_expr_executor, dwarf_evaluate_loc_desc and evaluate_for_locexpr_baton). Here is a short description of each class: - dwarf_expr_executor is evaluating a DWARF expression in a context of a Call Frame Information. The overridden methods of this subclass report an error if a specific DWARF operation, represented by that method, is not allowed in a CFI context. The source code of this subclass lacks the support for composite as well as implicit pointer location description. - dwarf_evaluate_loc_desc can evaluate any expression with no restrictions. All of the methods that this subclass overrides are actually doing what they are intended to do. This subclass contains a full support for all location description types. - evaluate_for_locexpr_baton subclass is a specialization of the dwarf_evaluate_loc_desc subclass and it's function is to add support for passed in buffers. This seems to be a way to go around the fact that DWARF standard lacks a bit offset support for memory location descriptions as well as using any location description for the push object address functionality. It all comes down to this question: what is a function of a DWARF expression evaluator? Is it to evaluate the expression in a given context or to check the correctness of that expression in that context? Currently, the only reason why there is a dwarf_expr_executor subclass is to report an invalid DWARF expression in a context of a CFI, but is that what the evaluator is supposed to do considering that the evaluator is not tied to a given DWARF version? There are more and more vendor and GNU extensions that are not part of the DWARF standard, so is it that impossible to expect that some of the extensions could actually lift the previously imposed restrictions of the CFI context? Not to mention that every new DWARF version is lifting some restrictions anyway. The thing that makes more sense for an evaluator to do, is to take the context of an evaluation and checks the requirements of every operation evaluated against that context. With this approach, the evaluator would report an error only if parts of the context, necessary for the evaluation, are missing. If this approach is taken, then the unification of the dwarf_evaluate_loc_desc, dwarf_expr_executor and dwarf_expr_context is the next logical step. This makes a design of the DWARF expression evaluator cleaner and allows more flexibility when supporting future vendor and GNU extensions. Additional benefit here is that now all evaluators have access to all location description types, which means that a vendor extended CFI rules could support composite location description as well. This also means that a new evaluator interface can be changed to return a single struct value (that describes the result of the evaluation) instead of a caller poking around the dwarf_expr_context internal data for answers (like it is done currently). This patch starts the merging process by moving the frame context information and support from dwarf_expr_executor and dwarf_evaluate_loc_desc to dwarf_expr_context evaluator. The idea is to report an error when a given operation requires a frame information to be resolved, if that information is not present. gdb/ChangeLog: * dwarf2/expr.c (ensure_have_frame): New function. (read_addr_from_reg): Add from frame.c. (dwarf_expr_context::dwarf_expr_context): Add frame info to dwarf_expr_context. (dwarf_expr_context::read_addr_from_reg): Remove. (dwarf_expr_context::get_reg_value): Move from dwarf_evaluate_loc_desc. (dwarf_expr_context::get_frame_base): Move from dwarf_evaluate_loc_desc. (dwarf_expr_context::execute_stack_op): Call frame context info check. Remove use of read_addr_from_reg method. * dwarf2/expr.h (struct dwarf_expr_context): Add frame info member, read_addr_from_reg, get_reg_value and get_frame_base declaration. (read_addr_from_reg): Move to expr.c. * dwarf2/frame.c (read_addr_from_reg): Move to dwarf_expr_context. (dwarf_expr_executor::read_addr_from_reg): Remove. (dwarf_expr_executor::get_frame_base): Remove. (dwarf_expr_executor::get_reg_value): Remove. (execute_stack_op): Use read_addr_from_reg function instead of read_addr_from_reg method. * dwarf2/loc.c (dwarf_evaluate_loc_desc::get_frame_base): Move to dwarf_expr_context. (dwarf_evaluate_loc_desc::get_reg_value): Move to dwarf_expr_context. (dwarf_evaluate_loc_desc::read_addr_from_reg): Remove. (dwarf2_locexpr_baton_eval):Use read_addr_from_reg function instead of read_addr_from_reg method.
2021-08-05Cleanup of the dwarf_expr_context constructorZoran Zaric2-18/+9
Move the initial values for dwarf_expr_context class data members to the class declaration in expr.h. gdb/ChangeLog: * dwarf2/expr.c (dwarf_expr_context::dwarf_expr_context): Remove initial data members values. * dwarf2/expr.h (dwarf_expr_context): Add initial values to the class data members.
2021-08-05Replace the symbol needs evaluator with a parserZoran Zaric6-116/+678
This patch addresses a design problem with the symbol_needs_eval_context class. It exposes the problem by introducing two new testsuite test cases. To explain the issue, I first need to explain the dwarf_expr_context class that the symbol_needs_eval_context class derives from. The intention behind the dwarf_expr_context class is to commonize the DWARF expression evaluation mechanism for different evaluation contexts. Currently in gdb, the evaluation context can contain some or all of the following information: architecture, object file, frame and compilation unit. Depending on the information needed to evaluate a given expression, there are currently three distinct DWARF expression evaluators:  - Frame: designed to evaluate an expression in the context of a call    frame information (dwarf_expr_executor class). This evaluator doesn't    need a compilation unit information.  - Location description: designed to evaluate an expression in the    context of a source level information (dwarf_evaluate_loc_desc    class). This evaluator expects all information needed for the    evaluation of the given expression to be present.  - Symbol needs: designed to answer a question about the parts of the    context information required to evaluate a DWARF expression behind a    given symbol (symbol_needs_eval_context class). This evaluator    doesn't need a frame information. The functional difference between the symbol needs evaluator and the others is that this evaluator is not meant to interact with the actual target. Instead, it is supposed to check which parts of the context information are needed for the given DWARF expression to be evaluated by the location description evaluator. The idea is to take advantage of the existing dwarf_expr_context evaluation mechanism and to fake all required interactions with the actual target, by returning back dummy values. The evaluation result is returned as one of three possible values, based on operations found in a given expression: - SYMBOL_NEEDS_NONE, - SYMBOL_NEEDS_REGISTERS and - SYMBOL_NEEDS_FRAME. The problem here is that faking results of target interactions can yield an incorrect evaluation result. For example, if we have a conditional DWARF expression, where the condition depends on a value read from an actual target, and the true branch of the condition requires a frame information to be evaluated, while the false branch doesn't, fake target reads could conclude that a frame information is not needed, where in fact it is. This wrong information would then cause the expression to be actually evaluated (by the location description evaluator) with a missing frame information. This would then crash the debugger. The gdb.dwarf2/symbol_needs_eval_fail.exp test introduces this scenario, with the following DWARF expression:                    DW_OP_addr $some_variable                    DW_OP_deref                    # conditional jump to DW_OP_bregx                    DW_OP_bra 4                    DW_OP_lit0                    # jump to DW_OP_stack_value                    DW_OP_skip 3                    DW_OP_bregx $dwarf_regnum 0                    DW_OP_stack_value This expression describes a case where some variable dictates the location of another variable. Depending on a value of some_variable, the variable whose location is described by this expression is either read from a register or it is defined as a constant value 0. In both cases, the value will be returned as an implicit location description on the DWARF stack. Currently, when the symbol needs evaluator fakes a memory read from the address behind the some_variable variable, the constant value 0 is used as the value of the variable A, and the check returns the SYMBOL_NEEDS_NONE result. This is clearly a wrong result and it causes the debugger to crash. The scenario might sound strange to some people, but it comes from a SIMD/SIMT architecture where $some_variable is an execution mask.  In any case, it is a valid DWARF expression, and GDB shouldn't crash while evaluating it. Also, a similar example could be made based on a condition of the frame base value, where if that value is concluded to be 0, the variable location could be defaulted to a TLS based memory address. The gdb.dwarf2/symbol_needs_eval_timeout.exp test introduces a second scenario. This scenario is a bit more abstract due to the DWARF assembler lacking the CFI support, but it exposes a different manifestation of the same problem. Like in the previous scenario, the DWARF expression used in the test is valid:                        DW_OP_lit1                        DW_OP_addr $some_variable                        DW_OP_deref                        # jump to DW_OP_fbreg                        DW_OP_skip 4                        DW_OP_drop                        DW_OP_fbreg 0                        DW_OP_dup                        DW_OP_lit0                        DW_OP_eq                        # conditional jump to DW_OP_drop                        DW_OP_bra -9                        DW_OP_stack_value Similarly to the previous scenario, the location of a variable A is an implicit location description with a constant value that depends on a value held by a global variable. The difference from the previous case is that DWARF expression contains a loop instead of just one branch. The end condition of that loop depends on the expectation that a frame base value is never zero. Currently, the act of faking the target reads will cause the symbol needs evaluator to get stuck in an infinite loop. Somebody could argue that we could change the fake reads to return something else, but that would only hide the real problem. The general impression seems to be that the desired design is to have one class that deals with parsing of the DWARF expression, while there are virtual methods that deal with specifics of some operations. Using an evaluator mechanism here doesn't seem to be correct, because the act of evaluation relies on accessing the data from the actual target with the possibility of skipping the evaluation of some parts of the expression. To better explain the proposed solution for the issue, I first need to explain a couple more details behind the current design: There are multiple places in gdb that handle DWARF expression parsing for different purposes. Some are in charge of converting the expression to some other internal representation (decode_location_expression, disassemble_dwarf_expression and dwarf2_compile_expr_to_ax), some are analysing the expression for specific information (compute_stack_depth_worker) and some are in charge of evaluating the expression in a given context (dwarf_expr_context::execute_stack_op and decode_locdesc). The problem is that all those functions have a similar (large) switch statement that handles each DWARF expression operation. The result of this is a code duplication and harder maintenance. As a step into the right direction to solve this problem (at least for the purpose of a DWARF expression evaluation) the expression parsing was commonized inside of an evaluator base class (dwarf_expr_context). This makes sense for all derived classes, except for the symbol needs evaluator (symbol_needs_eval_context) class. As described previously the problem with this evaluator is that if the evaluator is not allowed to access the actual target, it is not really evaluating. Instead, the desired function of a symbol needs evaluator seems to fall more into expression analysis category. This means that a more natural fit for this evaluator is to be a symbol needs analysis, similar to the existing compute_stack_depth_worker analysis. Another problem is that using a heavyweight mechanism of an evaluator to do an expression analysis seems to be an unneeded overhead. It also requires a more complicated design of the parent class to support fake target reads. The reality is that the whole symbol_needs_eval_context class can be replaced with a lightweight recursive analysis function, that will give more correct result without compromising the design of the dwarf_expr_context class. The analysis treats the expression byte stream as a DWARF operation graph, where each graph node can be visited only once and each operation can decide if the frame context is needed for their evaluation. The downside of this approach is adding of one more similar switch statement, but at least this way the new symbol needs analysis will be a lightweight mechnism and it will provide a correct result for any given DWARF expression. A more desired long term design would be to have one class that deals with parsing of the DWARF expression, while there would be a virtual methods that deal with specifics of some DWARF operations. Then that class would be used as a base for all DWARF expression parsing mentioned at the beginning. This however, requires a far bigger changes that are out of the scope of this patch series. The new analysis requires the DWARF location description for the argc argument of the main function to change in the assembly file gdb.python/amd64-py-framefilter-invalidarg.S. Originally, expression ended with a 0 value byte, which was never reached by the symbol needs evaluator, because it was detecting a stack underflow when evaluating the operation before. The new approach does not simulate a DWARF stack anymore, so the 0 value byte needs to be removed because it makes the DWARF expression invalid. gdb/ChangeLog: * dwarf2/loc.c (class symbol_needs_eval_context): Remove. (dwarf2_get_symbol_read_needs): New function. (dwarf2_loc_desc_get_symbol_read_needs): Remove. (locexpr_get_symbol_read_needs): Use dwarf2_get_symbol_read_needs. gdb/testsuite/ChangeLog: * gdb.python/amd64-py-framefilter-invalidarg.S : Update argc DWARF location expression. * lib/dwarf.exp (_location): Handle DW_OP_fbreg. * gdb.dwarf2/symbol_needs_eval.c: New file. * gdb.dwarf2/symbol_needs_eval_fail.exp: New file. * gdb.dwarf2/symbol_needs_eval_timeout.exp: New file.