diff options
| -rw-r--r-- | gdb/symtab.c | 94 |
1 files changed, 84 insertions, 10 deletions
diff --git a/gdb/symtab.c b/gdb/symtab.c index 63b780b..06b32c0 100644 --- a/gdb/symtab.c +++ b/gdb/symtab.c @@ -4157,6 +4157,9 @@ find_epilogue_using_linetable (CORE_ADDR func_addr) if (!find_pc_partial_function (func_addr, nullptr, &start_pc, &end_pc)) return {}; + /* While the standard allows for multiple points marked with epilogue_begin + in the same function, for performance reasons, this function will only + find the last address that sets this flag for a given block. */ const struct symtab_and_line sal = find_pc_line (start_pc, 0); if (sal.symtab != nullptr && sal.symtab->language () != language_asm) { @@ -4167,24 +4170,95 @@ find_epilogue_using_linetable (CORE_ADDR func_addr) = unrelocated_addr (end_pc - objfile->text_section_offset ()); const linetable *linetable = sal.symtab->linetable (); - /* This should find the last linetable entry of the current function. - It is probably where the epilogue begins, but since the DWARF 5 - spec doesn't guarantee it, we iterate backwards through the function - until we either find it or are sure that it doesn't exist. */ + if (linetable == nullptr || linetable->nitems == 0) + { + /* Empty line table. */ + return {}; + } + + /* Find the first linetable entry after the current function. Note that + this also may be an end_sequence entry. */ auto it = std::lower_bound (linetable->item, linetable->item + linetable->nitems, unrel_end, [] (const linetable_entry <e, unrelocated_addr pc) { return lte.unrelocated_pc () < pc; }); + if (it == linetable->item + linetable->nitems) + { + /* We couldn't find either: + - a linetable entry starting the function after the current + function, or + - an end_sequence entry that terminates the current function + at unrel_end. + + This can happen when the linetable doesn't describe the full + extent of the function. This can be triggered with: + - compiler-generated debug info, in the cornercase that the pc + with which we call find_pc_line resides in a different file + than unrel_end, or + - invalid dwarf assembly debug info. + In the former case, there's no point in iterating further, simply + return "not found". In the latter case, there's no current + incentive to attempt to support this, so handle this + conservatively and do the same. */ + return {}; + } - while (it->unrelocated_pc () >= unrel_start) - { - if (it->epilogue_begin) - return {it->pc (objfile)}; - it --; - } + if (unrel_end < it->unrelocated_pc ()) + { + /* We found a line entry that starts past the end of the + function. This can happen if the previous entry straddles + two functions, which shouldn't happen with compiler-generated + debug info. Handle the corner case conservatively. */ + return {}; + } + gdb_assert (unrel_end == it->unrelocated_pc ()); + + /* Move to the last linetable entry of the current function. */ + if (it == &linetable->item[0]) + { + /* Doing it-- would introduce undefined behaviour, avoid it by + explicitly handling this case. */ + return {}; + } + it--; + if (it->unrelocated_pc () < unrel_start) + { + /* Not in the current function. */ + return {}; + } + gdb_assert (it->unrelocated_pc () < unrel_end); + + /* We're at the the last linetable entry of the current function. This + is probably where the epilogue begins, but since the DWARF 5 spec + doesn't guarantee it, we iterate backwards through the current + function until we either find the epilogue beginning, or are sure + that it doesn't exist. */ + for (; it >= &linetable->item[0]; it--) + { + if (it->unrelocated_pc () < unrel_start) + { + /* No longer in the current function. */ + break; + } + + if (it->epilogue_begin) + { + /* Found the beginning of the epilogue. */ + return {it->pc (objfile)}; + } + + if (it == &linetable->item[0]) + { + /* No more entries in the current function. + Doing it-- would introduce undefined behaviour, avoid it by + explicitly handling this case. */ + break; + } + } } + return {}; } |