[llvm-bugs] [Bug 37125] New: [LLVM-COV] wrong coverage with builtin setjmp

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37125

            Bug ID: 37125
           Summary: [LLVM-COV] wrong coverage with builtin setjmp
           Product: Runtime Libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: libprofile library
          Assignee: unassignedbugs at nondot.org
          Reporter: yangyibiao at nju.edu.cn
                CC: llvm-bugs at lists.llvm.org

$ clang -v
clang version 7.0.0- (trunk)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.2.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8.0.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8.0.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

$ cat small.c
void *buf[5];

void fjmp (void) {
  __builtin_longjmp (buf, 1);
}

int main(void)
{
  int last = 0;

  if (__builtin_setjmp (buf) == 0) {
    __builtin_printf("True  branch\n");
    while (1) {
      last = 1;
      fjmp ();
    }
  } else {
    __builtin_printf("False branch\n");
  }

  return 0;
}

$ clang -w -O0 -g -fcoverage-mapping -fprofile-instr-generatesmall.profraw
small.c; ./a.out; llvm-profdata merge small.profraw -o small.profdata; llvm-cov
show a.out -instr-profile=small.profdata small.c > small.gcov; cat small.gcov
True  branch
False branch
    1|       |void *buf[5];
    2|       |
    3|      1|void fjmp (void) {
    4|      1|  __builtin_longjmp (buf, 1);
    5|      1|}
    6|       |
    7|       |int main(void)
    8|      1|{
    9|      1|  int last = 0;
   10|      1|
   11|      1|  if (__builtin_setjmp (buf) == 0) {
   12|      1|    __builtin_printf("True  branch\n");
   13|      2|    while (1) {
   14|      1|      last = 1;
   15|      1|      fjmp ();
   16|      1|    }
   17|      1|  } else {
   18|      0|    __builtin_printf("False branch\n");
   19|      0|  }
   20|      1|
   21|      1|  return 0;
   22|      1|}


Line #18 is wrongly marked as unexecuted. 
However, first call to builtin_setjmp is return 0. Therefore, the true block is
executed. Then, the fjmp() will execute longjmp and return a not zero value to
setjmp call site and execute the false branch. Thus, Line #18 should be marked
as executed. 

Line #13 is wrongly marked as executed twice. It should be marked as execute
only once.

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