GCC --Wdiv-by-zero false negative with `0 <= (f = 0) % e.b`
Closed this issue · 2 comments
0-0x41 commented
date: 2023-1-26
commit: 8c8ca873216387bc26046615c806b96f0345ff9d
args: -O0 -fanalyzer
test:
void __analyzer_eval();
union a
{
int b;
} c()
{
union a e;
int f;
e.b = 0;
if (0 <= (f = 0) % e.b)
{
__analyzer_eval(0 <= (f = 0) % e.b);
}
}
report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109200
fix:
original:
0-0x41 commented
GCC Static Analyzer does not generate a div-by-zero warning for the 0 <= (f = 0) % e.b
statement, but if it is changed to 0 <= (f = 0) % 0
, analyzer generates that warning.
See it live: https://godbolt.org/z/PYoroM8hx
void __analyzer_eval();
union a
{
int b;
} ;
void c(){
union a e;
int f;
e.b = 0;
if (0 <= (f = 0) % e.b)
// if (0 <= (f = 0) % 0)
{
__analyzer_eval(0 <= (f = 0) % e.b);
}
}
Output:
<source>: In function 'c':
<source>:14:5: warning: TRUE
14 | __analyzer_eval(0 <= (f = 0) % e.b);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Compiler returned: 0
Geoffrey1014 commented
duplicate of #51