[llvm-bugs] [Bug 45849] New: llvm-cov: macro constant in if expression lead to incorrect coverage

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45849

            Bug ID: 45849
           Summary: llvm-cov: macro constant in if expression lead to
                    incorrect coverage
           Product: Runtime Libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: libprofile library
          Assignee: unassignedbugs at nondot.org
          Reporter: yangyibiao at hust.edu.cn
                CC: llvm-bugs at lists.llvm.org

$ clang --version
clang version 11.0.0 (/home/yibiao/.cache/yay/llvm-git/llvm-project
871beba234a83a2a02da9dedbd59b91a1bfbd7af)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

$ clang -O0 -w -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.c.lcov; cat
small.c.lcov
    1|      1|#define N 6
    2|       |
    3|      1|int main() {
    4|      1|  if (10 < 6)
    5|      0|    return 1;
    6|      1|  if (10 < N)
    7|      1|    return 2;
    8|      1|}


N is a constant 6 which defined as macro in Line 1.
Line 7 is wrongly marked as executed. The execution count of Line 5 is correct. 

$ cat small.c
#define N 6

int main() {
  if (10 < 6)
    return 1;
  if (10 < N)
    return 2;
}

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