[PATCH] Fix producer string memory leaks

[Martin Sebor]

On 2/12/21 2:09 AM, Richard Biener via Gcc-patches wrote:
> On Thu, Feb 11, 2021 at 6:41 PM Martin Liška <mliska@suse.cz> wrote:
>>
>> Hello.
>>
>> This fixes 2 memory leaks I noticed.
>>
>> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>>
>> Ready to be installed?
> 
> OK.
> 
>> Thanks,
>> Martin
>>
>> gcc/ChangeLog:
>>
>>          * opts-common.c (decode_cmdline_option): Release werror_arg.
>>          * opts.c (gen_producer_string): Release output of
>>          gen_command_line_string.
>> ---
>>    gcc/opts-common.c | 1 +
>>    gcc/opts.c        | 7 +++++--
>>    2 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/gcc/opts-common.c b/gcc/opts-common.c
>> index 6cb5602896d..5e10edeb4cf 100644
>> --- a/gcc/opts-common.c
>> +++ b/gcc/opts-common.c
>> @@ -766,6 +766,7 @@ decode_cmdline_option (const char *const *argv, unsigned int lang_mask,
>>          werror_arg[0] = 'W';
>>
>>          size_t warning_index = find_opt (werror_arg, lang_mask);
>> +      free (werror_arg);

Sorry to butt in here, but since we're having a discussion on this
same subject in another review of a fix for a memory leak, I thought
I'd pipe up: I would suggest a better (more in line with C++ and more
future-proof) solution is to replace the call to xstrdup (and the need
to subsequently call free) with std::string.

>>          if (warning_index != OPT_SPECIAL_unknown)
>>          {
>>            const struct cl_option *warning_option
>> diff --git a/gcc/opts.c b/gcc/opts.c
>> index fc5f61e13cc..24bb64198c8 100644
>> --- a/gcc/opts.c
>> +++ b/gcc/opts.c
>> @@ -3401,8 +3401,11 @@ char *
>>    gen_producer_string (const char *language_string, cl_decoded_option *options,
>>                       unsigned int options_count)
>>    {
>> -  return concat (language_string, " ", version_string, " ",
>> -                gen_command_line_string (options, options_count), NULL);
>> +  char *cmdline = gen_command_line_string (options, options_count);
>> +  char *combined = concat (language_string, " ", version_string, " ",
>> +                          cmdline, NULL);
>> +  free (cmdline);
>> +  return combined;
>>    }

Here, changing gen_command_line_string() to return std::string instead
of a raw pointer would similarly avoid having to remember to free
the pointer (and forgetting).  The function has two other callers,
both in gcc/toplev.c, and both also leak the memory for the same
reason as here.

Martin

>>
>>    #if CHECKING_P
>> --
>> 2.30.0
>>