[Bug analyzer/107725] New: Spurious warning: use of uninitialized value with std::any

[Bug analyzer/107725] New: Spurious warning: use of uninitialized value with std::any

[cuzdav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107725

            Bug ID: 107725
           Summary: Spurious warning: use of uninitialized value with
                    std::any
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: cuzdav at gmail dot com
  Target Milestone: ---

Created attachment 53914
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53914&action=edit
preprocessed code

With the analyzer (-fanalyzer), this built cleanly with GCC10 and GCC11, but
starting with GCC 12 (still occurring in trunk) in either C++17 or c++20 mode,
I see this warning (x86 linux):

<source>:4:13: warning: use of uninitialized value '<unknown>' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
    4 |     return {};
      |             ^
  'std::any create()': events 1-2
    |
    |    3 | std::any create() {
    |      |                 ^
    |      |                 |
    |      |                 (1) region created on stack here
    |    4 |     return {};
    |      |             ~    
    |      |             |
    |      |             (2) use of uninitialized value '<unknown>' here
    |
Compiler returned: 0


This is the code in its entirety:

    #include <any>
    std::any create() {
        return {};
    }

https://godbolt.org/z/TWPcaW4Kn

[Bug analyzer/107725] Spurious warning: use of uninitialized value with std::any

[cuzdav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107725

--- Comment #1 from Chris Uzdavinis <cuzdav at gmail dot com> ---
I get a similar warning with this code.  Unsure if it's the same underlying
issue.  Also does not warn with g++10 or g++11, but does with newer versions.

#include <sstream>
#include <string>

std::string create() {
    std::ostringstream oss;
    return oss.str();
}


https://godbolt.org/z/cz66zhKn5

<source>:6:20: warning: use of uninitialized value '<unknown>' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
    6 |     return oss.str();
      |                    ^
  'std::string create()': events 1-2
    |
    |    4 | std::string create() {
    |      |                    ^
    |      |                    |
    |      |                    (1) region created on stack here
    |    5 |     std::ostringstream oss;
    |    6 |     return oss.str();
    |      |                    ~
    |      |                    |
    |      |                    (2) use of uninitialized value '<unknown>' here

[Bug analyzer/107725] Spurious warning: use of uninitialized value with std::any

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107725

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

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

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
C++ isn't supported by the analyzer yet.  I hope to address this in GCC 14, but
it's not going to give useful results on C++ before then.

Sorry about this.

Marked as NEW and added to the analyzer-c++ tracker, to tackle in GCC 14.


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/107725] Spurious warning: use of uninitialized value with std::any

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107725

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-11-16
     Ever confirmed|0                           |1

[Bug analyzer/107725] Spurious warning: use of uninitialized value with std::any

[cuzdav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107725

--- Comment #3 from Chris Uzdavinis <cuzdav at gmail dot com> ---
Ah, sorry I didn't realize that.  Its use was suggested by Jason Turner in his
most recent C++ Weekly so I started to give it a try.  Perhaps there will be an
influx of such premature reports since it was put on the radar.

[Bug analyzer/107725] Spurious warning: use of uninitialized value with std::any

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107725

--- Comment #4 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Aha thanks: presumably "Ep 350 - The Right Way to Write C++ Code in 2022"?  
I'm watching it now.