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This commit is the result of running the gdb/copyright.py script,
which automated the update of the copyright year range for all
source files managed by the GDB project to be updated to include
year 2023.
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This commit brings all the changes made by running gdb/copyright.py
as per GDB's Start of New Year Procedure.
For the avoidance of doubt, all changes in this commits were
performed by the script.
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When I run test-case gdb.dwarf2/dw2-abs-hi-pc.exp with gcc, we have:
...
(gdb) break hello^M
Breakpoint 1 at 0x4004c0: file dw2-abs-hi-pc-hello.c, line 24.^M
(gdb) PASS: gdb.dwarf2/dw2-abs-hi-pc.exp: break hello
...
but with clang, I run into:
...
(gdb) break hello^M
Breakpoint 1 at 0x4004e4^M
(gdb) FAIL: gdb.dwarf2/dw2-abs-hi-pc.exp: break hello
...
The problem is that the CU and function both have an empty address range:
...
<0><d2>: Abbrev Number: 1 (DW_TAG_compile_unit)
<108> DW_AT_name : dw2-abs-hi-pc-hello.c
<123> DW_AT_low_pc : 0x4004e0
<127> DW_AT_high_pc : 0x4004e0
<1><12f>: Abbrev Number: 2 (DW_TAG_subprogram)
<131> DW_AT_name : hello
<13a> DW_AT_low_pc : 0x4004e0
<13e> DW_AT_high_pc : 0x4004e0
...
The address ranges are set like this in dw2-abs-hi-pc-hello-dbg.S:
...
.4byte .hello_start /* DW_AT_low_pc */
.4byte .hello_end /* DW_AT_high_pc */
...
where the labels refer to dw2-abs-hi-pc-hello.c:
...
extern int v;
asm (".hello_start: .globl .hello_start\n");
void
hello (void)
{
asm (".hello0: .globl .hello0\n");
v++;
asm (".hello1: .globl .hello1\n");
}
asm (".hello_end: .globl .hello_end\n");
...
Using asm labels in global scope is a known source of problems, as explained
in the comment of proc function_range in gdb/testsuite/lib/dwarf.exp.
Fix this by using function_range instead.
Tested on x86_64-linux with gcc and clang-7 and clang-12.
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This commits the result of running gdb/copyright.py as per our Start
of New Year procedure...
gdb/ChangeLog
Update copyright year range in copyright header of all GDB files.
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gdb/ChangeLog:
Update copyright year range in all GDB files.
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This commit applies all changes made after running the gdb/copyright.py
script.
Note that one file was flagged by the script, due to an invalid
copyright header
(gdb/unittests/basic_string_view/element_access/char/empty.cc).
As the file was copied from GCC's libstdc++-v3 testsuite, this commit
leaves this file untouched for the time being; a patch to fix the header
was sent to gcc-patches first.
gdb/ChangeLog:
Update copyright year range in all GDB files.
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gdb/ChangeLog:
Update copyright year range in all GDB files
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This applies the second part of GDB's End of Year Procedure, which
updates the copyright year range in all of GDB's files.
gdb/ChangeLog:
Update copyright year range in all GDB files.
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gdb/ChangeLog:
Update year range in copyright notice of all files.
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gdb/ChangeLog:
Update year range in copyright notice of all files.
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Starting with DWARF version 4, the description of the DW_AT_high_pc
attribute was amended to say:
if it is of class constant, the value is an unsigned integer offset
which when added to the low PC gives the address of the first
location past the last instruction associated with the entity.
A change was made in Apr 27th, 2012 to reflect that change:
| commit 91da14142c0171e58a91ad58a32fd010b700e761
| Author: Mark Wielaard <mjw@redhat.com>
| Date: Fri Apr 27 18:55:19 2012 +0000
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| * dwarf2read.c (dwarf2_get_pc_bounds): Check DW_AT_high_pc form to
| see whether it is an address or a constant offset from DW_AT_low_pc.
| (dwarf2_record_block_ranges): Likewise.
| (read_partial_die): Likewise.
Unfortunately, this new interpretation is now used regardless of
the CU's DWARF version. It turns out that one of WindRiver's compilers
(FTR: Diabdata 4.4) is generating DWARF version 2 info with
DW_AT_high_pc attributes improperly using the data4 form. Because of
that, we miscompute all high PCs incorrectly. This leads to a lot of
symtabs having overlapping ranges, which in turn causes havoc in
pc-to-symtab-and-line translations.
One visible effect is when inserting a breakpoint on a given function:
(gdb) b world
Breakpoint 1 at 0x4005c4
The source location of the breakpoint is missing. The output should be:
(gdb) b world
Breakpoint 1 at 0x4005c8: file dw2-rel-hi-pc-world.c, line 24.
What happens in this case is that the pc-to-SAL translation first
starts be trying to find the symtab associated to our PC using
each symtab's ranges. Because of the high_pc miscomputation,
many symtabs end up matching, and the heuristic trying to select
the most probable one unfortunately returns one that is unrelated
(it really had no change in this case to do any better). Once we
have the wrong symtab, the start searching the associated linetable,
where the addresses are correct, thus finding no match, and therefore
no SAL.
This patch is an attempt at handling the situation as gracefully
as we can, without guarantees. It introduces a new function
"attr_value_as_address" which uses the correct accessor for getting
the value of a given attribute. It then adjust the code throughout
this unit to use this function instead of assuming that addresses always
have the DW_FORM_addr format.
It also fixes the original issue of miscomputing the high_pc
by limiting the new interpretation of constant form DW_AT_high_pc
attributes to units using DWARF version 4 or later.
gdb/ChangeLog:
* dwarf2read.c (attr_value_as_address): New function.
(dwarf2_find_base_address, read_call_site_scope): Use
attr_value_as_address in place of DW_ADDR.
(dwarf2_get_pc_bounds): Use attr_value_as_address to get
the low and high addresses. Slight rework of the handling
of the high pc being a constant form, and limit it to
DWARF verson 4 or higher.
(dwarf2_record_block_ranges): Likewise.
(read_partial_die): Likewise.
(new_symbol_full): Use attr_value_as_address in place of DW_ADDR.
gdb/testsuite/ChangeLog:
* gdb.dwarf2/dw2-abs-hi-pc-hello-dbg.S: New file.
* gdb.dwarf2/dw2-abs-hi-pc-hello.c: New file.
* gdb.dwarf2/dw2-abs-hi-pc-world-dbg.S: New file.
* gdb.dwarf2/dw2-abs-hi-pc-world.c: New file.
* gdb.dwarf2/dw2-abs-hi-pc.c: New file.
* gdb.dwarf2/dw2-abs-hi-pc.exp: New file.
Tested on x86_64-linux.
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