https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120485
Bug ID: 120485
Summary: Superfluous branch coverage and condition coverage
before preprocessor directives
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: gcov-profile
Assignee: unassigned at gcc dot gnu.org
Reporter: wentaoz5 at illinois dot edu
Target Milestone: ---
Hit the issue when measuring coverage for
https://sources.debian.org/src/mawk/1.3.4.20200120-3.1/parse.c/#L1832
How to reproduce:
$ gcc --version
gcc (GCC) 16.0.0 20250511 (experimental)
Copyright (C) 2025 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 > test1.c << 'EOF'
int g;
int foo(int a, int b) {
#include "header.h"
return g;
}
int main(void) {
for (int i = 0; i < 1; i++)
foo(0, 0);
for (int i = 0; i < 20; i++)
foo(1, 0);
for (int i = 0; i < 300; i++)
foo(0, 1);
for (int i = 0; i < 4000; i++)
foo(1, 1);
}
EOF
$ cat > header.h << EOF
if (a && b)
g++;
EOF
$ gcc --coverage -fcondition-coverage test1.c -o test1
$ ./test1
$ gcov -b -c --condition test1
$ cat header.h.gcov
...
4321: 1: if (a && b)
branch 0 taken 4020 (fallthrough)
branch 1 taken 301
branch 2 taken 4000 (fallthrough)
branch 3 taken 20
condition outcomes covered 4/4
4000: 2: g++;
...
$ cat test.c.gcov
...
4321: 2:int foo(int a, int b) {
branch 0 taken 4020 (fallthrough)
branch 1 taken 301
condition outcomes covered 4/4
-: 3:#include "header.h"
4321: 4: return g;
-: 5:}
...
Branch and condition coverage for "a && b" is correctly shown in
header.h.gcov, but a copy of condition coverage and an incomplete copy of
branch coverage are incorrectly put after line 2 of test.c before
"#include".
Different ways of manifestation are possible, e.g.
8040: 1: if (a && b)
branch 0 taken 8000 (fallthrough)
branch 1 taken 40
8000: 2: return 0;
642: 3: return 1;
17284: 1:int foo(int a, int b) {
branch 0 taken 8040 (fallthrough)
branch 1 taken 602
branch 2 taken 8040 (fallthrough)
branch 3 taken 602
condition outcomes covered 4/4
condition outcomes covered 4/4
-: 2:#include "header.h"
-: 3:}
This time two copies of condition coverage are both presented for the same
file.
A probably more common pattern is parser generated code, like in the mawk
example.
$ cat > this.c << EOF
int g;
int foo(int a, int b) {
#line 4 "the-same.c"
if (a && b)
g++;
#line 7 "this.c"
}
int main(void) {
for (int i = 0; i < 1; i++)
foo(0, 0);
for (int i = 0; i < 20; i++)
foo(1, 0);
for (int i = 0; i < 300; i++)
foo(0, 1);
for (int i = 0; i < 4000; i++)
foo(1, 1);
}
EOF
$ cp this.c the-same.c
$ gcc --coverage -fcondition-coverage this.c -o this
$ ./this
$ gcov -b -c --condition this
$ cat this.c.gcov
...
8642: 2:int foo(int a, int b) {
branch 0 taken 8040 (fallthrough)
branch 1 taken 602
condition outcomes covered 4/4
-: 3:#line 4 "the-same.c"
-: 4: if (a && b)
-: 5: g++;
-: 6:#line 7 "this.c"
8642: 7:}
...
The symptom is the same: extra branch and condition coverage is reported
after line 2.
