https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117412
Bug ID: 117412
Summary: Bogus execution count for assignment with function
call
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: gcov-profile
Assignee: unassigned at gcc dot gnu.org
Reporter: wentaoz5 at illinois dot edu
Target Milestone: ---
How to reproduce:
$ gcc --version
gcc (GCC) 15.0.0 20240923 (experimental)
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ cat > test.c << 'EOF'
int foo(long a) {
return 0;
};
struct Bar { int b; };
int main(void) {
int x[100];
struct Bar y;
int z;
int a1;
unsigned long a2;
long long a3;
*x = foo(
a1*2);
x[1] = foo(
a2+1);
y.b = foo(
a3-3);
return 0;
}
EOF
$ gcc --coverage test.c -o test
$ ./test
$ gcov test
$ cat test.c.gcov
...
-: 15:
2: 16: *x = foo(
1: 17: a1*2);
-: 18:
2: 19: x[1] = foo(
1: 20: a2+1);
-: 21:
2: 22: y.b = foo(
1: 23: a3-3);
-: 24:
1: 25: return 0;
...
Line 16, 19 and 22 are reported to executed twice, which is hard to interpret.
(Example reduced from
https://github.com/apache/httpd/blob/2.4.62/server/util_filter.c#L138)
These are the known conditions to trigger the behavior:
1. The argument is "somewhat complex": variable alone or constant alone
won't trigger it
2. Function name and assignment is put in the first line; operator of the
argument is put in the second line
3. Argument and parameter have different types
4. The return value is assigned to one of {subscript,dereference,struct member}
