[gdb] Use partial symbol table to find language for main
When language is set to auto, part of loading an executable is to update the
language accordingly. This is implemented by set_initial_language.
The implementation of set_initial_language works as follows:
- check if any objfile in the progspace has name_of_main/language_of_main
set, and if so, use the first one found. [ This is what you get f.i. when
using dwarf with DW_AT_main_subprogram. ]
- otherwise, check for known names in the minimal symbols, and either:
- use the associated language if any (f.i. for ada), or
- lookup the symbol in the symtab for the name and use the symbol language
(f.i. for c/c++).
The symbol lookup can be slow though.
In the case of the cc1 binary from PR23710 comment 1, getting to the initial
prompt takes ~8s:
...
$ time.sh gdb cc1 -batch -ex "show language"
The current source language is "auto; currently c++".
maxmem: 1272260
real: 8.05
user: 7.73
system: 0.38
...
but if we skip guessing the initial language by setting it instead, it takes
only ~4s:
...
$ time.sh gdb -iex "set language c++" cc1 -batch -ex "show language"
The current source language is "c++".
maxmem: 498272
real: 3.99
user: 3.90
system: 0.15
...
In both cases, we load the partial symbols for the executable, but in the
first case only we also do a lookup of main, which causes the corresponding
partial symtab to be expanded into a full symtab.
Ideally, we'd like to get the language of the symbol without triggering
expansion into a full symtab, and get the speedup without having to set the
language manually.
There's a related fixme in the header comment of set_initial_language:
...
/* Set the initial language.
FIXME: A better solution would be to record the language in the
psymtab when reading partial symbols, and then use it (if known) to
set the language. This would be a win for formats that encode the
language in an easily discoverable place, such as DWARF. For
stabs, we can jump through hoops looking for specially named
symbols or try to intuit the language from the specific type of
stabs we find, but we can't do that until later when we read in
full symbols. */
void
set_initial_language (void)
...
Since we're already tracking the language of partial symbols, use this to set
the language for the main symbol.
Note that this search in partial symbol tables is not guaranteed to yield the
same result as the lookup_symbol_in_language call currently done in
set_initial_language. I'm not sure if that matters.
Build and reg-tested on x86_64-linux.
This requires an update to test-case gdb.base/break-interp.exp to work around
PR25613 - "[gdb] verbose message appears not at start of line during
backtrace".
gdb/ChangeLog:
2020-03-04 Tom de Vries <tdevries@suse.de>
* dwarf2/read.c (dwarf2_gdb_index_functions,
* dwarf2_debug_names_functions): Init lookup_symbol_language with NULL.
* psymtab.c (psym_lookup_symbol_language): New function.
(psym_functions): Init psym_lookup_symbol_language with
psym_lookup_symbol_language.
* psymtab.h (psym_lookup_symbol_language): Declare.
* symfile-debug.c (debug_sym_quick_functions): Init
lookup_symbol_language with NULL.
* symfile.c (set_initial_language): Remove fixme comment.
* symfile.h (struct quick_symbol_functions): Add
lookup_symbol_language.
* symtab.c (find_quick_symbol_language): New function.
(find_main_name): Use find_quick_symbol_language.
* symtab.h (find_quick_symbol_language): Declare.
gdb/testsuite/ChangeLog:
2020-03-04 Tom de Vries <tdevries@suse.de>
* gdb.base/break-interp.exp: Set verbose back to off.
* gdb.base/c-linkage-name.exp (verify_psymtab_expanded): Move ...
* lib/gdb.exp: ... here.
* gdb.base/main-psymtab.exp: New file.
---
gdb/dwarf2/read.c | 2 ++
gdb/psymtab.c | 35 ++++++++++++++++++++++++++++
gdb/psymtab.h | 5 ++++
gdb/symfile-debug.c | 1 +
gdb/symfile.c | 11 +--------
gdb/symfile.h | 14 ++++++++++++
gdb/symtab.c | 38 +++++++++++++++++++++++++++++++
gdb/symtab.h | 4 ++++
gdb/testsuite/gdb.base/break-interp.exp | 2 ++
gdb/testsuite/gdb.base/c-linkage-name.exp | 13 -----------
gdb/testsuite/gdb.base/main-psymtab.exp | 34 +++++++++++++++++++++++++++
gdb/testsuite/lib/gdb.exp | 13 +++++++++++
12 files changed, 149 insertions(+), 23 deletions(-)
@@ -4801,6 +4801,7 @@ const struct quick_symbol_functions dwarf2_gdb_index_functions =
dw2_forget_cached_source_info,
dw2_map_symtabs_matching_filename,
dw2_lookup_symbol,
+ NULL,
dw2_print_stats,
dw2_dump,
dw2_expand_symtabs_for_function,
@@ -5683,6 +5684,7 @@ const struct quick_symbol_functions dwarf2_debug_names_functions =
dw2_forget_cached_source_info,
dw2_map_symtabs_matching_filename,
dw2_debug_names_lookup_symbol,
+ NULL,
dw2_print_stats,
dw2_debug_names_dump,
dw2_debug_names_expand_symtabs_for_function,
@@ -517,6 +517,40 @@ psym_lookup_symbol (struct objfile *objfile,
return stab_best;
}
+/* Psymtab version of lookup_symbol_language. See its definition in
+ the definition of quick_symbol_functions in symfile.h. */
+
+enum language
+psym_lookup_symbol_language (struct objfile *objfile,
+ block_enum block_index,
+ const char *name,
+ domain_enum domain,
+ bool *symbol_found_p)
+{
+ *symbol_found_p = false;
+ if (objfile->sf == NULL)
+ return language_unknown;
+ const int psymtab_index = (block_index == GLOBAL_BLOCK ? 1 : 0);
+
+ lookup_name_info lookup_name (name, symbol_name_match_type::FULL);
+
+ for (partial_symtab *ps : require_partial_symbols (objfile, true))
+ {
+ struct partial_symbol *psym;
+ if (ps->readin_p ())
+ continue;
+
+ psym = lookup_partial_symbol (objfile, ps, name, psymtab_index, domain);
+ if (psym)
+ {
+ *symbol_found_p = true;
+ return psym->ginfo.language ();
+ }
+ }
+
+ return language_unknown;
+}
+
/* Returns true if PSYM matches LOOKUP_NAME. */
static bool
@@ -1452,6 +1486,7 @@ const struct quick_symbol_functions psym_functions =
psym_forget_cached_source_info,
psym_map_symtabs_matching_filename,
psym_lookup_symbol,
+ psym_lookup_symbol_language,
psym_print_stats,
psym_dump,
psym_expand_symtabs_for_function,
@@ -151,4 +151,9 @@ extern const struct quick_symbol_functions dwarf2_debug_names_functions;
extern psymtab_storage::partial_symtab_range require_partial_symbols
(struct objfile *objfile, bool verbose);
+enum language psym_lookup_symbol_language (struct objfile *objfile,
+ block_enum block_index,
+ const char *name,
+ domain_enum domain,
+ bool *symbol_found_p);
#endif /* PSYMTAB_H */
@@ -362,6 +362,7 @@ static const struct quick_symbol_functions debug_sym_quick_functions =
debug_qf_forget_cached_source_info,
debug_qf_map_symtabs_matching_filename,
debug_qf_lookup_symbol,
+ NULL,
debug_qf_print_stats,
debug_qf_dump,
debug_qf_expand_symtabs_for_function,
@@ -1667,16 +1667,7 @@ symbol_file_command (const char *args, int from_tty)
}
}
-/* Set the initial language.
-
- FIXME: A better solution would be to record the language in the
- psymtab when reading partial symbols, and then use it (if known) to
- set the language. This would be a win for formats that encode the
- language in an easily discoverable place, such as DWARF. For
- stabs, we can jump through hoops looking for specially named
- symbols or try to intuit the language from the specific type of
- stabs we find, but we can't do that until later when we read in
- full symbols. */
+/* Set the initial language. */
void
set_initial_language (void)
@@ -183,6 +183,20 @@ struct quick_symbol_functions
const char *name,
domain_enum domain);
+ /* Check to see if the symbol is defined in a "partial" symbol table
+ of OBJFILE. BLOCK_INDEX should be either GLOBAL_BLOCK or STATIC_BLOCK,
+ depending on whether we want to search global symbols or static
+ symbols. NAME is the name of the symbol to look for. DOMAIN
+ indicates what sort of symbol to search for.
+
+ If found, sets *symbol_found_p to true and returns the symbol language.
+ defined, or NULL if no such symbol table exists. */
+ enum language (*lookup_symbol_language) (struct objfile *objfile,
+ block_enum block_index,
+ const char *name,
+ domain_enum domain,
+ bool *symbol_found_p);
+
/* Print statistics about any indices loaded for OBJFILE. The
statistics should be printed to gdb_stdout. This is used for
"maint print statistics". */
@@ -2560,6 +2560,34 @@ lookup_symbol_in_objfile (struct objfile *objfile, enum block_enum block_index,
return result;
}
+/* Find the language for partial symbol with NAME. */
+
+enum language
+find_quick_symbol_language (block_enum block_index, const char *name,
+ const domain_enum domain)
+{
+ for (objfile *objfile : current_program_space->objfiles ())
+ {
+ if (objfile->sf && objfile->sf->qf
+ && objfile->sf->qf->lookup_symbol_language)
+ continue;
+ return language_unknown;
+ }
+
+ for (objfile *objfile : current_program_space->objfiles ())
+ {
+ bool symbol_found_p;
+ enum language lang
+ = objfile->sf->qf->lookup_symbol_language (objfile, block_index, name,
+ domain, &symbol_found_p);
+ if (!symbol_found_p)
+ continue;
+ return lang;
+ }
+
+ return language_unknown;
+}
+
/* Private data to be used with lookup_symbol_global_iterator_cb. */
struct global_or_static_sym_lookup_data
@@ -6090,6 +6118,16 @@ find_main_name (void)
/* The languages above didn't identify the name of the main procedure.
Fallback to "main". */
+
+ /* Try to find language for main in psymtabs. */
+ enum language lang
+ = find_quick_symbol_language (GLOBAL_BLOCK, "main", VAR_DOMAIN);
+ if (lang != language_unknown)
+ {
+ set_main_name ("main", lang);
+ return;
+ }
+
set_main_name ("main", language_unknown);
}
@@ -2349,4 +2349,8 @@ private:
std::vector<bound_minimal_symbol> m_minimal_symbols;
};
+enum language
+find_quick_symbol_language (block_enum block_index, const char *name,
+ const domain_enum domain);
+
#endif /* !defined(SYMTAB_H) */
@@ -251,6 +251,7 @@ proc test_core {file displacement} {
if ![regexp {^(NONE|FOUND-.*)$} $displacement] {
fail $test_displacement
}
+ gdb_test_no_output "set verbose off"
gdb_test "bt" "#\[0-9\]+ +\[^\r\n\]*\\mlibfunc\\M\[^\r\n\]*\r\n#\[0-9\]+ +\[^\r\n\]*\\mmain\\M.*" "core main bt"
}
@@ -301,6 +302,7 @@ proc test_attach_gdb {file pid displacement prefix} {
if ![regexp {^(NONE|FOUND-.*)$} $displacement] {
fail $test_displacement
}
+ gdb_test_no_output "set verbose off"
gdb_test "bt" "#\[0-9\]+ +\[^\r\n\]*\\mlibfunc\\M\[^\r\n\]*\r\n#\[0-9\]+ +\[^\r\n\]*\\mmain\\M.*" "attach main bt"
gdb_exit
@@ -27,19 +27,6 @@ if { [gdb_compile "${sources}" "${binfile}" executable {debug}] != "" } {
clean_restart ${binfile}
-# Verify that partial symtab expansion for $filename has state $readin
-
-proc verify_psymtab_expanded { filename readin } {
- set cmd "maint info psymtab"
- set test "$cmd: $filename: $readin"
- set re [multi_line \
- " \{ psymtab \[^\r\n\]*$filename\[^\r\n\]*" \
- " readin $readin" \
- ".*"]
-
- gdb_test $cmd $re $test
-}
-
# Verify that partial symtab expansion has not taken place for
# c-linkage-name-2.c.
new file mode 100644
@@ -0,0 +1,34 @@
+# Copyright 2020 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile persistent-lang.cc
+
+if {[build_executable "failed to prepare" $testfile $srcfile debug]} {
+ return -1
+}
+
+clean_restart
+
+set auto_cpp \
+ {The current source language is "auto; currently c\+\+"\.}
+
+gdb_load ${binfile}
+gdb_test "show language" $auto_cpp \
+ "language auto/c++ after load"
+
+# Verify that partial symtab expansion has not taken place for
+# persistent-lang.cc
+
+verify_psymtab_expanded persistent-lang.cc no
@@ -6902,5 +6902,18 @@ gdb_caching_proc skip_ctf_tests {
} executable "additional_flags=-gt"]
}
+# Verify that partial symtab expansion for $filename has state $readin.
+
+proc verify_psymtab_expanded { filename readin } {
+ set cmd "maint info psymtab"
+ set test "$cmd: $filename: $readin"
+ set re [multi_line \
+ " \{ psymtab \[^\r\n\]*$filename\[^\r\n\]*" \
+ " readin $readin" \
+ ".*"]
+
+ gdb_test $cmd $re $test
+}
+
# Always load compatibility stuff.
load_lib future.exp