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From: Tom Tromey <tromey@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] Ignore 0,0 entries in .debug_aranges Date: Thu, 14 Apr 2022 18:27:01 +0000 (GMT) [thread overview] Message-ID: <20220414182701.0E2473857C6F@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=1a7c41d5ece7d0d1aa77d8019ee46f03181854fa commit 1a7c41d5ece7d0d1aa77d8019ee46f03181854fa Author: Tom Tromey <tromey@adacore.com> Date: Thu Apr 14 09:36:09 2022 -0600 Ignore 0,0 entries in .debug_aranges When running the internal AdaCore test suite against the new DWARF indexer, I found one regression on RISC-V. The test in question uses --gc-sections, and winds up with an entry in the middle of a .debug_aranges that has both address and length of 0. In this scenario, gdb assumes the entries are terminated and then proceeds to reject the section because it reads a subsequent entry as if it were a header. It seems to me that, because each header describes the size of each .debug_aranges CU, it's better to simply ignore 0,0 entries and simply read to the end. That is what this patch does. I've patched an existing test to provide a regression test for this. Diff: --- gdb/dwarf2/read.c | 11 +++++++++-- gdb/testsuite/gdb.dwarf2/locexpr-data-member-location.exp | 3 +++ 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index 698720276a9..6dcd446e5f4 100644 --- a/gdb/dwarf2/read.c +++ b/gdb/dwarf2/read.c @@ -2469,7 +2469,7 @@ read_addrmap_from_aranges (dwarf2_per_objfile *per_objfile, bytes. */ addr += (entry_end - addr) % (2 * address_size); - for (;;) + while (addr < entry_end) { if (addr + 2 * address_size > entry_end) { @@ -2487,7 +2487,14 @@ read_addrmap_from_aranges (dwarf2_per_objfile *per_objfile, dwarf5_byte_order); addr += address_size; if (start == 0 && length == 0) - break; + { + /* This can happen on some targets with --gc-sections. + This pair of values is also used to mark the end of + the entries for a given CU, but we ignore it and + instead handle termination using the check at the top + of the loop. */ + continue; + } if (start == 0 && !per_bfd->has_section_at_zero) { /* Symbol was eliminated due to a COMDAT group. */ diff --git a/gdb/testsuite/gdb.dwarf2/locexpr-data-member-location.exp b/gdb/testsuite/gdb.dwarf2/locexpr-data-member-location.exp index 67e96fb1128..adb4e0a4c21 100644 --- a/gdb/testsuite/gdb.dwarf2/locexpr-data-member-location.exp +++ b/gdb/testsuite/gdb.dwarf2/locexpr-data-member-location.exp @@ -296,6 +296,9 @@ Dwarf::assemble ${asm_file} { } aranges {} cu_label { + # This 0,0 entry tests that the .debug_aranges reader can + # handle an apparent terminator before the end of the ranges. + arange {} 0 0 arange {} $foo_start $foo_end arange {} $bar_start $bar_end }
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