The following code generates a warning when using GCC analyzer, but I don't think the warning is valid.

struct Guard {
    ~this() {}
}
Guard lock() {
    return Guard();
}
void bar() {
    auto foo = lock();
}

Compiled with GCC version 13.1:

$ gdc -fanalyzer test.d -O2 -c
test.d: In function 'lock':
test.d:5:5: warning: use of uninitialized value 'MEM[(unsigned char * {ref-all})&D.3438]' [CWE-457] [-Wanalyzer-use-of-uninitialized-value]
    5 |     return Guard();
      |     ^
  'lock': events 1-2
    |
    |    5 |     return Guard();
    |      |     ^
    |      |     |
    |      |     (1) region created on stack here
    |      |     (2) use of uninitialized value 'MEM[(unsigned char * {ref-all})&D.3438]' here
    |

Any ideas? Thanks!

On Thursday, 31 August 2023 at 13:53:55 UTC, Zachary Yedidia wrote:

struct Guard {
    ~this() {}
}
Guard lock() {
    return Guard();
}
void bar() {
    auto foo = lock();
}

$ gdc -fanalyzer test.d -O2 -c
test.d: In function 'lock':
test.d:5:5: warning: use of uninitialized value 'MEM[(unsigned char * {ref-all})&D.3438]' [CWE-457] [-Wanalyzer-use-of-uninitialized-value]
    5 |     return Guard();
      |     ^
  'lock': events 1-2
    |
    |    5 |     return Guard();
    |      |     ^
    |      |     |
    |      |     (1) region created on stack here
    |      |     (2) use of uninitialized value 'MEM[(unsigned char * {ref-all})&D.3438]' here
    |

Hi,

Thanks for posting this!

Had a quick poke around - also with a C++ equivalent test - and it looks like GCC's static analyzer is not good at dealing with returning non-trivially copyable struct via NRVO.

I'll have a prod a bit more later, but my first instinct would be to raise a bug report with GCC.

On Thursday, 31 August 2023 at 13:53:55 UTC, Zachary Yedidia wrote:

struct Guard {
    ~this() {}
}
Guard lock() {
    return Guard();
}
void bar() {
    auto foo = lock();
}

I'm at the GNU Cauldron, and David has just said "don't use -fanalyzer on C++ in GCC 13, you will get rubbish out of it". This would also extend to all other languages that aren't C too.

The good news is that things are going to be improved in GCC 14.