Re: [PATCH][gdb/symtab] Fix language of duplicate static minimal symbol

[Tom de Vries <tdevries at suse dot de>]

On 10/30/18 10:21 PM, Keith Seitz wrote:
> On 10/30/18 12:11 PM, Tom de Vries wrote:
>> However, when we use gdb to print info on foo, both foos are listed, but we
>> get one symbol mangled and one symbol demangled:
>> ...
>> $ gdb ./a.out -batch -ex "info func foo"
>> All functions matching regular expression "foo":
>>
>> Non-debugging symbols:
>> 0x00000000004004c7  foo()
>> 0x00000000004004dd  _ZL3foov
>> ...
>>
> 
> Good catch!
> >> Build and reg-tested on x86_64-linux.
>>
>> OK for trunk?
> 
> I have just a few comments.
> 
>> 2018-10-30  Tom de Vries  <tdevries@suse.de>
>>
>> 	* symtab.c (symbol_set_names): Call symbol_find_demangled_name
>> 	unconditionally, to get the language of the symbol.
> 
> s/get/set/ ? When reading the patch, I originally wondered how that would help,
> but symbol_find_demangled_name actually *sets* the gsymbol's language if
> it is language_auto.
> 

Typo fixed.

>>
>> 	* gdb.base/msym.c: New test.
>> 	* gdb.base/msym.exp: New file.
>> 	* gdb.base/msym_main.c: New test.
> 
> These entries should be listed under the testsuite ChangeLog, like:
> 
> testsuite/ChangeLog:
> YYYY-MM-DD ....
> 
> 	* gdb.xyz/file1.c: ...
> 	* gdb.xyz/file1.exp: ....
> 
> [https://sourceware.org/gdb/wiki/ContributionChecklist#Properly_Formatted_GNU_ChangeLog]
> 

I have a pre-commit script (for both gcc and gdb) that uses this format,
and puts ChangeLog hunks in the correct ChangeLog file ( more detail
here: https://sourceware.org/ml/gdb-patches/2018-06/msg00351.html ).
Sofar this format has been acceptable for maintainers.

> "msym.c" et al aren't particularly descriptive, though. Can we devise a better,
> more explicit name? Something along the lines of "multiple-language-msyms.exp".
> It's long, but it describes things better. [I'm not saying you should use
> this name, but something other than just "msym.{c,exp}".]
> 

Renamed to msym-lang.exp et al.

> Sorry, some of that is kinda nitpicky.
> 

Np, I'm still kinda new to gdb, all input appreciated.

>> diff --git a/gdb/symtab.c b/gdb/symtab.c
>> index cd27a75e8c..481428f733 100644
>> --- a/gdb/symtab.c
>> +++ b/gdb/symtab.c
>> @@ -818,6 +818,10 @@ symbol_set_names (struct general_symbol_info *gsymbol,
>>    else
>>      linkage_name_copy = linkage_name;
>>  
>> +  /* Set the symbol language.  */
>> +  char *demangled_name = symbol_find_demangled_name (gsymbol,
>> +						     linkage_name_copy);
>> +
>>    entry.mangled = linkage_name_copy;
>>    slot = ((struct demangled_name_entry **)
>>  	  htab_find_slot (per_bfd->demangled_names_hash,
> 
> symbol_find_demangled_name returns a malloc'd string which will leak here unless
> the code goes through the branch. You'll need to save the result into a
> unique_xmalloc_ptr and adjust the code accordingly.
> 

Done, thanks for pointing that out.

> Otherwise, LGTM. Thanks very much for the patch.
> 

And thanks for the review.

Re-tested as attached.

Thanks,
- Tom

[gdb/symtab] Fix language of duplicate static minimal symbol

Consider a test-case with source files msym.c:
...
static int foo (void) { return 1; }
...
and msym_main.c:
...
static int foo (void) { return 2; }
int main (void) { return 0; }
..
compiled as c++ with minimal symbols:
...
$ g++ msym_main.c msym.c
...

With objdump -x we find the two foo symbols prefixed with their corresponding
files in the symbol table:
...
0000000000000000 l    df *ABS*  0000000000000000              msym_main.c
00000000004004c7 l     F .text  000000000000000b              _ZL3foov
0000000000000000 l    df *ABS*  0000000000000000              msym.c
00000000004004dd l     F .text  000000000000000b              _ZL3foov
...

However, when we use gdb to print info on foo, both foos are listed, but we
get one symbol mangled and one symbol demangled:
...
$ gdb ./a.out -batch -ex "info func foo"
All functions matching regular expression "foo":

Non-debugging symbols:
0x00000000004004c7  foo()
0x00000000004004dd  _ZL3foov
...

During minimal symbol reading symbol_set_names is called for each symbol.

First, it's called with foo from msym.c, an entry is created in
per_bfd->demangled_names_hash and symbol_find_demangled_name is called, which
has the side effect of setting the language of the symbol to language_cplus.

Then, it's called with foo from msym_main.c.  Since
per_bfd->demangled_names_hash already has an entry for that name,
symbol_find_demangled_name is not called, and the language of the symbol
remains language_auto.

Fix this by doing the symbol_find_demangled_name call unconditionally.

Build and reg-tested on x86_64-linux.

2018-10-30  Tom de Vries  <tdevries@suse.de>

	* symtab.c (symbol_set_names): Call symbol_find_demangled_name
	unconditionally, to set the language of the symbol.  Manage freeing
	returned pointer using gdb::unique_xmalloc_ptr.

	* gdb.base/msym-lang.c: New test.
	* gdb.base/msym-lang.exp: New file.
	* gdb.base/msym-lang-main.c: New test.

---
 gdb/symtab.c                            | 14 +++++++-------
 gdb/testsuite/gdb.base/msym-lang-main.c | 28 ++++++++++++++++++++++++++++
 gdb/testsuite/gdb.base/msym-lang.c      | 22 ++++++++++++++++++++++
 gdb/testsuite/gdb.base/msym-lang.exp    | 25 +++++++++++++++++++++++++
 4 files changed, 82 insertions(+), 7 deletions(-)

diff --git a/gdb/symtab.c b/gdb/symtab.c
index cd27a75e8c..aee4c0c710 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -818,6 +818,11 @@ symbol_set_names (struct general_symbol_info *gsymbol,
   else
     linkage_name_copy = linkage_name;
 
+  /* Set the symbol language.  */
+  char *demangled_name_ptr
+    = symbol_find_demangled_name (gsymbol, linkage_name_copy);
+  gdb::unique_xmalloc_ptr<char> demangled_name (demangled_name_ptr);
+
   entry.mangled = linkage_name_copy;
   slot = ((struct demangled_name_entry **)
 	  htab_find_slot (per_bfd->demangled_names_hash,
@@ -830,9 +835,7 @@ symbol_set_names (struct general_symbol_info *gsymbol,
       || (gsymbol->language == language_go
 	  && (*slot)->demangled[0] == '\0'))
     {
-      char *demangled_name = symbol_find_demangled_name (gsymbol,
-							 linkage_name_copy);
-      int demangled_len = demangled_name ? strlen (demangled_name) : 0;
+      int demangled_len = demangled_name ? strlen (demangled_name.get ()) : 0;
 
       /* Suppose we have demangled_name==NULL, copy_name==0, and
 	 linkage_name_copy==linkage_name.  In this case, we already have the
@@ -870,10 +873,7 @@ symbol_set_names (struct general_symbol_info *gsymbol,
 	}
 
       if (demangled_name != NULL)
-	{
-	  strcpy ((*slot)->demangled, demangled_name);
-	  xfree (demangled_name);
-	}
+	strcpy ((*slot)->demangled, demangled_name.get());
       else
 	(*slot)->demangled[0] = '\0';
     }
diff --git a/gdb/testsuite/gdb.base/msym-lang-main.c b/gdb/testsuite/gdb.base/msym-lang-main.c
new file mode 100644
index 0000000000..f093f71ca4
--- /dev/null
+++ b/gdb/testsuite/gdb.base/msym-lang-main.c
@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 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/>.  */
+
+static int
+foo (void)
+{
+  return 2;
+}
+
+int
+main (void)
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/msym-lang.c b/gdb/testsuite/gdb.base/msym-lang.c
new file mode 100644
index 0000000000..c9610154dd
--- /dev/null
+++ b/gdb/testsuite/gdb.base/msym-lang.c
@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 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/>.  */
+
+static int
+foo (void)
+{
+  return 1;
+}
diff --git a/gdb/testsuite/gdb.base/msym-lang.exp b/gdb/testsuite/gdb.base/msym-lang.exp
new file mode 100644
index 0000000000..993225c9d6
--- /dev/null
+++ b/gdb/testsuite/gdb.base/msym-lang.exp
@@ -0,0 +1,25 @@
+# Copyright (C) 2018 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 msym-lang-main.c msym-lang.c
+
+if {[prepare_for_testing "failed to prepare" $testfile [list $srcfile $srcfile2] \
+	 {c++}]} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+gdb_test "info func foo" ".* foo\\(\\).* foo\\(\\).*"