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* [Bug symtab/30841] New: [gdb, symtab] gdb-add-index doesn't support .gnu_debugaltlink
@ 2023-09-12 9:41 vries at gcc dot gnu.org
2023-09-12 9:42 ` [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index vries at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: vries at gcc dot gnu.org @ 2023-09-12 9:41 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=30841
Bug ID: 30841
Summary: [gdb, symtab] gdb-add-index doesn't support
.gnu_debugaltlink
Product: gdb
Version: HEAD
Status: NEW
Severity: enhancement
Priority: P2
Component: symtab
Assignee: unassigned at sourceware dot org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
Say we have an executable a.out, with a .gnu_debugaltlink to a dwz file a.dwz.
Adding a .gdb_index section to a.out also requires adding a minimal .gdb_index
section to a.dwz.
Our current implementation of gdb-add-index, based on the "save gdb-index"
command (which currently only generates a symbol-file.gdb-index) doesn't
support this.
Supporting this would involve:
- modifying "save gdb-index" to also generate a symbol-file.dwz-gdb-index,
and
- modifying gdb-add-index to add that as a .gdb_section to the file pointed to
by the .gnu_debugaltlink.
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index 2023-09-12 9:41 [Bug symtab/30841] New: [gdb, symtab] gdb-add-index doesn't support .gnu_debugaltlink vries at gcc dot gnu.org @ 2023-09-12 9:42 ` vries at gcc dot gnu.org 2023-09-12 15:46 ` tromey at sourceware dot org ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: vries at gcc dot gnu.org @ 2023-09-12 9:42 UTC (permalink / raw) To: gdb-prs https://sourceware.org/bugzilla/show_bug.cgi?id=30841 Tom de Vries <vries at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|[gdb, symtab] gdb-add-index |[gdb, symtab] support |doesn't support |.gnu_debugaltlink in |.gnu_debugaltlink |gdb-add-index -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index 2023-09-12 9:41 [Bug symtab/30841] New: [gdb, symtab] gdb-add-index doesn't support .gnu_debugaltlink vries at gcc dot gnu.org 2023-09-12 9:42 ` [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index vries at gcc dot gnu.org @ 2023-09-12 15:46 ` tromey at sourceware dot org 2023-09-12 16:25 ` vries at gcc dot gnu.org ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: tromey at sourceware dot org @ 2023-09-12 15:46 UTC (permalink / raw) To: gdb-prs https://sourceware.org/bugzilla/show_bug.cgi?id=30841 Tom Tromey <tromey at sourceware dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |tromey at sourceware dot org --- Comment #1 from Tom Tromey <tromey at sourceware dot org> --- My recollection is that in 'dwz -m' mode, all symbols from PUs should be attributed to one of their containing CUs, and that the separate file should not require an index. -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index 2023-09-12 9:41 [Bug symtab/30841] New: [gdb, symtab] gdb-add-index doesn't support .gnu_debugaltlink vries at gcc dot gnu.org 2023-09-12 9:42 ` [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index vries at gcc dot gnu.org 2023-09-12 15:46 ` tromey at sourceware dot org @ 2023-09-12 16:25 ` vries at gcc dot gnu.org 2023-09-13 3:18 ` sam at gentoo dot org 2023-09-13 6:53 ` vries at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: vries at gcc dot gnu.org @ 2023-09-12 16:25 UTC (permalink / raw) To: gdb-prs https://sourceware.org/bugzilla/show_bug.cgi?id=30841 --- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> --- (In reply to Tom Tromey from comment #1) > My recollection is that in 'dwz -m' mode, all symbols from > PUs should be attributed to one of their containing CUs, Yes. That doesn't cover the case of a CU in the dwz file though. > and that the separate file should not require an index. That was added in this commit: ... commit c4973306879b6079bdfc997474a2cbbd89f49bd2 Author: Simon Marchi <simon.marchi@polymtl.ca> Date: Sun Jun 16 10:13:56 2019 -0400 Write index for dwz -m file PR 24445 ("dwz multifile index not written to index cache") exposed the fact that we are not doing things right when we generate an index for an object file that has is linked to a dwz file. The same happens whether the index is generated with the intent of populating the index cache or using the save gdb-index command. The problem can be observed when running these tests with the cc-with-dwz-m board: FAIL: gdb.base/index-cache.exp: test_cache_enabled_hit: check index-cache stats FAIL: gdb.dwarf2/gdb-index.exp: index used FAIL: gdb.dwarf2/gdb-index.exp: index used after symbol reloading When generating the index for such file and inspecting the CU list of the resulting index (with readelf --debug-dump=gdb_index), we can see something like: CU table: [ 0] 0x0 - 0xb9 [ 1] 0x0 - 0x44 This is supposed to be a sorted list of the ranges of all CUs in the file this index represents, so already having some overlap is a red flag. It turns out that we save the ranges of CUs coming from both the main file and the dwz file in the same index. After digging a little bit, it became quite obvious that the index in the main file should only list the CUs present in the main file, and a separate index should be generated for the dwz file, listing the CUs present in that file. First, that's what happens if you run dwz on a file that already has a GDB index embedded. Second, dwarf2read.c has code to read an index from a dwz file. The index in the dwz file is actually required to be present, if the main file has an index. So this patch changes write_psymtabs_to_index to generate an index for the dwz file, if present. That index only contains a CU list, just like what the dwz tool does when processing a file that already contains an index. Some notes about the implementation: - The file management (creating a temp file, make sure it's close/removed on error - in the right order) is a bit heavy in write_psymtabs_to_index, and I needed to add a third file. I factored this pattern in a separate class, index_wip_file. - It became a bit tedious to keep the call to assert_file_size in write_psymtabs_to_index, write_gdbindex would have had to return two sizes. Instead, I moved the calls to assert_file_size where the file is written. The downside is that we lose the filename at this point, but it was only used for the very improbable case of ftell failing, so I think it's not a problem. - The actual writing of the index file is factored out to write_gdbindex_1, so it can be re-used for both index files. - While the "save gdb-index" command will now write two .gdb-index files, this patch does not update the gdb-add-index.sh script, this will come in a later patch. ... -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index 2023-09-12 9:41 [Bug symtab/30841] New: [gdb, symtab] gdb-add-index doesn't support .gnu_debugaltlink vries at gcc dot gnu.org ` (2 preceding siblings ...) 2023-09-12 16:25 ` vries at gcc dot gnu.org @ 2023-09-13 3:18 ` sam at gentoo dot org 2023-09-13 6:53 ` vries at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: sam at gentoo dot org @ 2023-09-13 3:18 UTC (permalink / raw) To: gdb-prs https://sourceware.org/bugzilla/show_bug.cgi?id=30841 Sam James <sam at gentoo dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |sam at gentoo dot org -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index 2023-09-12 9:41 [Bug symtab/30841] New: [gdb, symtab] gdb-add-index doesn't support .gnu_debugaltlink vries at gcc dot gnu.org ` (3 preceding siblings ...) 2023-09-13 3:18 ` sam at gentoo dot org @ 2023-09-13 6:53 ` vries at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: vries at gcc dot gnu.org @ 2023-09-13 6:53 UTC (permalink / raw) To: gdb-prs https://sourceware.org/bugzilla/show_bug.cgi?id=30841 --- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> --- (In reply to Tom de Vries from comment #2) > (In reply to Tom Tromey from comment #1) > > My recollection is that in 'dwz -m' mode, all symbols from > > PUs should be attributed to one of their containing CUs, > > Yes. That doesn't cover the case of a CU in the dwz file though. > See also https://sourceware.org/git/?p=dwz.git;a=commit;h=b7111689a2ccec2f57343f1051ec8f1df5e89e5c -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-09-13 6:53 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-09-12 9:41 [Bug symtab/30841] New: [gdb, symtab] gdb-add-index doesn't support .gnu_debugaltlink vries at gcc dot gnu.org 2023-09-12 9:42 ` [Bug symtab/30841] [gdb, symtab] support .gnu_debugaltlink in gdb-add-index vries at gcc dot gnu.org 2023-09-12 15:46 ` tromey at sourceware dot org 2023-09-12 16:25 ` vries at gcc dot gnu.org 2023-09-13 3:18 ` sam at gentoo dot org 2023-09-13 6:53 ` vries at gcc dot gnu.org
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