| Issue |
149769
|
| Summary |
[LLVM-COV] The use of the global variable errno leads an incorrect coverage statistic.
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
8ss-boop
|
llvm version:
clang version 21.0.0git (https://github.com/llvm/llvm-project.git 872eac7af0050813062baba9662beb81093b6b55)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /root/software/llvm-releases/llvm-0704/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/12
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/12
Candidate multilib: .;@m64
Selected multilib: .;@m64
```c
#include <stdatomic.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
int main() {
atomic_int ai = 42;
int i = 0;
volatile int flag = 1;
while (flag) {
switch (i++) {
case 0:
if (atomic_fetch_add(&ai, 1) >= 45)
flag = 0;
break;
case 1:
if (atomic_load(&ai) % 2 == 0)
errno = EDOM;
else
errno = ERANGE;
break;
case 2:
if (errno != EDOM && errno != ERANGE)
flag = 0;
break;
default:
flag = 0;
}
}
printf("Final atomic value: %d\n", atomic_load(&ai));
return atomic_load(&ai);
}
```
for the program above, we got the following coverage report from llvm-cov
```
/*
clang -std=c2x -lm -fcoverage-mapping -fprofile-instr-generate test.c
./a.out
llvm-profdata merge default.profraw -o default.profdata;
llvm-cov show --show-line-counts -instr-profile="" ./a.out > test.c.lcov
*/
1| |#include <stdatomic.h>
2| |#include <errno.h>
3| |#include <stdlib.h>
4| |#include <stdio.h>
5| 1|int main() {
6| 1| atomic_int ai = 42;
7| 1| int i = 0;
8| 1| volatile int flag = 1;
9| 5| while (flag) {
10| 4| switch (i++) {
11| 1| case 0:
12| 1| if (atomic_fetch_add(&ai, 1) >= 45)
13| 0| flag = 0;
14| 1| break;
15| 1| case 1:
16| 1| if (atomic_load(&ai) % 2 == 0)
17| 1| errno = EDOM;
18| 1| else
19| 1| errno = ERANGE;
20| 1| break;
21| 1| case 2:
22| 1| if (errno != EDOM && errno != ERANGE)
23| 0| flag = 0;
24| 1| break;
25| 1| default:
26| 1| flag = 0;
27| 4| }
28| 4| }
29| 1| printf("Final atomic value: %d\n", atomic_load(&ai));
30| | return atomic_load(&ai);
31| 1|}
```
the output is:
```
Final atomic value: 43
```
Line 19 was actually executed instead of line 17.
![]()
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
