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From: "xdje42 at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug c++/17687] New: linear search in cp_add_using_directive
Date: Sun, 07 Dec 2014 22:29:00 -0000 [thread overview]
Message-ID: <bug-17687-4717@http.sourceware.org/bugzilla/> (raw)
https://sourceware.org/bugzilla/show_bug.cgi?id=17687
Bug ID: 17687
Summary: linear search in cp_add_using_directive
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: c++
Assignee: unassigned at sourceware dot org
Reporter: xdje42 at gmail dot com
Filing this to remember a potential perf issue.
I noticed this while debugging another issue.
I had set a breakpoint on cp_add_using_directive and saw it being called once
for each symbol thusly:
(top-gdb) c
Continuing.
Breakpoint 3, cp_add_using_directive (dest=0x7ffff0659462 "std",
src=0x866f92 "", alias=0x0, declaration=0x7ffff05f5eb1 "clearerr",
excludes=0x0, copy_names=0, obstack=0x16285f0)
at ../../anon-ns-16874/gdb/cp-namespace.c:139
(top-gdb)
Continuing.
Breakpoint 3, cp_add_using_directive (dest=0x7ffff0659462 "std",
src=0x866f92 "", alias=0x0, declaration=0x7ffff05f71ce "fclose",
excludes=0x0, copy_names=0, obstack=0x16285f0)
at ../../anon-ns-16874/gdb/cp-namespace.c:139
(top-gdb)
Continuing.
Breakpoint 3, cp_add_using_directive (dest=0x7ffff0659462 "std",
src=0x866f92 "", alias=0x0, declaration=0x7ffff05f97dd "feof",
excludes=0x0, copy_names=0, obstack=0x16285f0)
at ../../anon-ns-16874/gdb/cp-namespace.c:139
(top-gdb)
Continuing.
Breakpoint 3, cp_add_using_directive (dest=0x7ffff0659462 "std",
src=0x866f92 "", alias=0x0, declaration=0x7ffff05f8356 "ferror",
excludes=0x0, copy_names=0, obstack=0x16285f0)
at ../../anon-ns-16874/gdb/cp-namespace.c:139
(top-gdb)
Continuing.
Breakpoint 3, cp_add_using_directive (dest=0x7ffff0659462 "std",
src=0x866f92 "", alias=0x0, declaration=0x7ffff05fb494 "fflush",
excludes=0x0, copy_names=0, obstack=0x16285f0)
at ../../anon-ns-16874/gdb/cp-namespace.c:139
(top-gdb)
Is this a potential perf issue?
[both when reading debug info and later when doing lookups]
(top-gdb) bt
#0 cp_add_using_directive (dest=0x7ffff0659462 "std", src=0x866f92 "",
alias=0x0, declaration=0x7ffff06562d6 "mbstate_t", excludes=0x0,
copy_names=0, obstack=0x16285f0)
at ../../anon-ns-16874/gdb/cp-namespace.c:139
#1 0x000000000062e254 in read_import_statement (die=0x1798f70, cu=0x16af3e0)
at ../../anon-ns-16874/gdb/dwarf2read.c:8896
#2 0x000000000062ce73 in process_die (die=0x1798f70, cu=0x16af3e0)
at ../../anon-ns-16874/gdb/dwarf2read.c:8234
#3 0x000000000063b3e0 in read_namespace (die=0x1798e30, cu=0x16af3e0)
at ../../anon-ns-16874/gdb/dwarf2read.c:13898
#4 0x000000000062cd92 in process_die (die=0x1798e30, cu=0x16af3e0)
at ../../anon-ns-16874/gdb/dwarf2read.c:8217
#5 0x000000000062e78b in read_file_scope (die=0x17d0290, cu=0x16af3e0)
at ../../anon-ns-16874/gdb/dwarf2read.c:9057
#6 0x000000000062cc90 in process_die (die=0x17d0290, cu=0x16af3e0)
at ../../anon-ns-16874/gdb/dwarf2read.c:8164
#7 0x000000000062c53e in process_full_comp_unit (per_cu=0x1627f40,
pretend_language=language_minimal)
at ../../anon-ns-16874/gdb/dwarf2read.c:7946
#8 0x000000000062b4ee in process_queue ()
at ../../anon-ns-16874/gdb/dwarf2read.c:7484
#9 0x00000000006207cc in dw2_do_instantiate_symtab (per_cu=0x1627f40)
at ../../anon-ns-16874/gdb/dwarf2read.c:2638
#10 0x000000000062085e in dw2_instantiate_symtab (per_cu=0x1627f40)
at ../../anon-ns-16874/gdb/dwarf2read.c:2659
#11 0x0000000000622f9a in dw2_lookup_symbol (objfile=0x1628590, block_index=0,
name=0x1490640 "(anonymous namespace)",
domain=VAR_DOMAIN) at ../../anon-ns-16874/gdb/dwarf2read.c:3612
#12 0x000000000059ac9c in lookup_symbol_via_quick_fns (
objfile=objfile@entry=0x1628590, block_index=block_index@entry=0,
name=name@entry=0x1490640 "(anonymous namespace)",
domain=domain@entry=VAR_DOMAIN) at ../../anon-ns-16874/gdb/symtab.c:1679
...
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next reply other threads:[~2014-12-07 22:29 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-07 22:29 xdje42 at gmail dot com [this message]
2014-12-07 22:30 ` [Bug c++/17687] " xdje42 at gmail dot com
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