[llvm-bugs] [Bug 49421] New: [LLVM-COV] Dead code was marked as executed

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49421

            Bug ID: 49421
           Summary: [LLVM-COV] Dead code was marked as executed
           Product: Runtime Libraries
           Version: 11.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: libprofile library
          Assignee: unassignedbugs at nondot.org
          Reporter: cnwy1996 at outlook.com
                CC: llvm-bugs at lists.llvm.org

$ clang -v
clang version 11.0.0
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/wangyang/llvm-project/build/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

$ cat test.c

#include <stdio.h>
int main() {
  FILE *f = fopen("conftest.out", "w");
  return ferror(f) || fclose(f) != 0;
  printf("passed");
  return 0;
}

$ clang -w -O0 -g -fcoverage-mapping -fprofile-instr-generate=test.profraw
test.c; ./a.out; llvm-profdata merge test.profraw -o test.profdata; llvm-cov
show a.out -instr-profile=test.profdata test.c > test.lcov; cat test.lcov
    1|       |#include <stdio.h>
    2|      1|int main() {
    3|      1|  FILE *f = fopen("conftest.out", "w");
    4|      1|  return ferror(f) || fclose(f) != 0;
    5|      1|  printf("passed");
    6|      0|  return 0;
    7|      1|}

line 5 was wrongly marked as executed.

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