https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108725
Bug ID: 108725
Summary: -Wanalyzer-use-of-uninitialized-value on ternary
pointer access seen in qemu-7.2.0's dump/win_dump.c
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: dmalcolm at gcc dot gnu.org
Target Milestone: ---
Created attachment 54438
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54438&action=edit
Reproducer
We get two false positives from the attached at -O1 and above, with both trunk
and gcc 12:
Trunk: https://godbolt.org/z/KboceYY7q
GCC 12.2: https://godbolt.org/z/jEPa6vaPd
<source>: In function 'cpu_read_ptr':
<source>:15:24: warning: use of uninitialized value 'ptr64' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
15 | *ptr = x64 ? ptr64 : ptr32;
| ~~~~~~~~~~~~^~~~~~~
'cpu_read_ptr': events 1-5
|
| 11 | uint64_t ptr64;
| | ^~~~~
| | |
| | (1) region created on stack here
| | (2) capacity: 8 bytes
|......
| 15 | *ptr = x64 ? ptr64 : ptr32;
| | ~~~~~~~~~~~~~~~~~~~
| | |
| | (3) following 'true' branch (when 'x64 !=
0')...
| | (4) ...to here
| | (5) use of uninitialized value 'ptr64' here
|
<source>:15:24: warning: use of uninitialized value 'ptr32' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
15 | *ptr = x64 ? ptr64 : ptr32;
| ~~~~~~~~~~~~^~~~~~~
'cpu_read_ptr': events 1-5
|
| 10 | uint32_t ptr32;
| | ^~~~~
| | |
| | (1) region created on stack here
| | (2) capacity: 4 bytes
|......
| 15 | *ptr = x64 ? ptr64 : ptr32;
| | ~~~~~~~~~~~~~~~~~~~
| | |
| | (3) following 'false' branch (when 'x64 ==
0')...
| | (4) ...to here
| | (5) use of uninitialized value 'ptr32' here
|
Compiler returned: 0
where the analyzer isn't treating the argument pointer as potentially having
been written through (presumably confused by the ternary operator).
