https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108745
Bug ID: 108745
Summary: -Wanalyzer-deref-before-check false positives seen in
ImageMagick due to checks in macros
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 54441
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54441&action=edit
Reproducer
Am seeing lots of false positives from -Wanalyzer-deref-before-check on
ImageMagick on code like this:
if ((image->columns == 0) || (image->rows == 0))
ThrowReaderException("MustSpecifyImageSize");
return image;
where ThrowReaderException has an "if (image)" embedded within it:
https://godbolt.org/z/74d1aoqTa
<source>: In function 'ReadMAPImage':
<source>:38:6: warning: check of 'image' for NULL after already dereferencing
it [-Wanalyzer-deref-before-check]
38 | if ((image) != (Image *) NULL) \
| ^
<source>:52:5: note: in expansion of macro 'ThrowReaderException'
52 | ThrowReaderException("MustSpecifyImageSize");
| ^~~~~~~~~~~~~~~~~~~~
'ReadMAPImage': event 1
|
| 51 | if ((image->columns == 0) || (image->rows == 0))
| | ~~~~~^~~~~~~~~
| | |
| | (1) pointer 'image' is dereferenced here
|
'ReadMAPImage': event 2
|
| 38 | if ((image) != (Image *) NULL) \
| | ^
| | |
| | (2) pointer 'image' is checked for NULL here but it was
already dereferenced at (1)
<source>:52:5: note: in expansion of macro 'ThrowReaderException'
| 52 | ThrowReaderException("MustSpecifyImageSize");
| | ^~~~~~~~~~~~~~~~~~~~
|
Compiler returned: 0
Presumably we shouldn't warn if the check is hidden inside a macro.
