[llvm-bugs] [Bug 35556] New: [LLVM-COV] dead label and false conditional lead to incorrect coverage in llvm-cov

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=35556

            Bug ID: 35556
           Summary: [LLVM-COV] dead label and false conditional lead to
                    incorrect coverage in llvm-cov
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: yangyibiao at nju.edu.cn
                CC: llvm-bugs at lists.llvm.org

$ clang -v
clang version 6.0.0-svn319926-1~exp1 (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/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/6.3.0
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/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/6.3.0
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
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

$ cat small.c
int main()
{
    int i = 0;
    if (1)
    {
        goto lbl;
lbl_dead:
        i++;
lbl:
        if (0) 
            ;
        i++;
    }
}

$ clang -w -O0 -g -fcoverage-mapping -fprofile-instr-generate=small.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
    1|       |int main()
    2|      1|{
    3|      1|    int i = 0;
    4|      1|    if (1)
    5|      1|    {
    6|      1|        goto lbl;
    7|      0|lbl_dead:
    8|      0|        i++;
    9|      1|lbl:
   10|      1|        if (0) 
   11|      0|            ;
   12|      0|        i++;
   13|      0|    }
   14|      1|}


As we can find that, Line #12 was wrongly marked as not executed.

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