[Bug analyzer/108879] New: -Wanalyzer-malloc-leak false positive stl string in try catch block

[Bug analyzer/108879] New: -Wanalyzer-malloc-leak false positive stl string in try catch block

[jg at jguk dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108879

            Bug ID: 108879
           Summary: -Wanalyzer-malloc-leak false positive stl string in
                    try catch block
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: jg at jguk dot org
  Target Milestone: ---

Tested just now on gcc (trunk). Source code below and the output.

https://godbolt.org/z/Ms6fezGvT

<source>: In function 'void make_string(const char*, std::string&)':
<source>:11:27: warning: leak of
'<anonymous>.std::__cxx11::basic_string<char>::_M_dataplus.std::__cxx11::basic_string<char>::_Alloc_hider::_M_p'
[CWE-401] [-Wanalyzer-malloc-leak]
   11 |         out_string = std::string(str);
      |                           ^~~~~~~~~~~
  'void make_string(const char*, std::string&)': events 1-2
    |
    |    7 | void make_string(const char * const str, std::string & out_string)
    |      |      ^~~~~~~~~~~
    |      |      |
    |      |      (1) entry to 'make_string'
    |......
    |   11 |         out_string = std::string(str);
    |      |                           ~~~~~~~~~~~
    |      |                           |
    |      |                           (2) calling
'std::__cxx11::basic_string<char>::basic_string<>' from 'make_string'





// -fanalyzer -std=c++23 -O1 -Wall -Wno-analyzer-use-of-uninitialized-value

#include <string>
#include <cstdio>

void make_string(const char * const str, std::string & out_string)
{
    try
    {
        out_string = std::string(str);
    }
    catch (std::exception& ex)
    {
        printf("exception %s\n", ex.what());
        fflush(stdout);
    }
}

int main()
{
    std::string str;
    make_string(NULL, str);
}

[Bug analyzer/108879] -Wanalyzer-malloc-leak false positive stl string in try catch block

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108879

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |97110

--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Yeah, I haven't implemented exceptions yet, so even the simplest cases are
likely to fail :-/

I plan to spent a chunk of my GCC *14* cycles working on C++ support (in the
hope of "eating my own dogfood" for GCC 14), but in the meantime, I'm afraid
it's not going to be helpful to file any more bugs about -fanalyzer on C++.

I've added a caveat about that to the GCC 13 release notes:
https://gcc.gnu.org/git/?p=gcc-wwwdocs.git;a=commitdiff;h=98c77c7cd4fc3f1bb1e77e260640cbbe5fd45b46

and to the manpage/docs:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=a90316c6ceddfbb47b3c2161baf446ccb87df5ff


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97110
[Bug 97110] [meta-bug] tracker bug for supporting C++ in -fanalyzer

[Bug analyzer/108879] -Wanalyzer-malloc-leak false positive stl string in try catch block

[jg at jguk dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108879

--- Comment #2 from Jonny Grant <jg at jguk dot org> ---
(In reply to David Malcolm from comment #1)
> Yeah, I haven't implemented exceptions yet, so even the simplest cases are
> likely to fail :-/
> 
> I plan to spent a chunk of my GCC *14* cycles working on C++ support (in the
> hope of "eating my own dogfood" for GCC 14), but in the meantime, I'm afraid
> it's not going to be helpful to file any more bugs about -fanalyzer on C++.
> 
> I've added a caveat about that to the GCC 13 release notes:
> https://gcc.gnu.org/git/?p=gcc-wwwdocs.git;a=commitdiff;
> h=98c77c7cd4fc3f1bb1e77e260640cbbe5fd45b46
> 
> and to the manpage/docs:
> https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;
> h=a90316c6ceddfbb47b3c2161baf446ccb87df5ff

Many thanks for you reply. Looking forward to trying out in future GCC
releases! thank you for working on such useful features.