https://bugs.llvm.org/show_bug.cgi?id=50722
Bug ID: 50722
Summary: Add warnings about violation of aliasing rules
Product: clang
Version: 12.0
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: C
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected],
[email protected]
The following, rather horrible code (which came off a Usenet discussion)
violates C aliasing rules in several places:
#include <stdio.h>
typedef unsigned char uchar;
int
main ()
{
double d = 2.34;
int i[2];
printf ("%lf\n", d);
*(long *)i = *(long *)&d;
((int *)&d)[0] = i[0];
((int *)&d)[1] = i[1];
printf ("%.15lf\n", d);
((uchar *)&d)[2] += 123;
printf ("%.15lf\n", d);
return 0;
}
It would be nice if clang could warn or issue an error about the lines
*(long *)i = *(long *)&d;
*(long *)i = *(long *)&d;
((int *)&d)[0] = i[0];
with suitable options (preferably -Wall).
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