[llvm-bugs] [Bug 37001] New: [LLVM-COV] a pointer assignment after the return statement is wrongly marked as executed in llvm-cov

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37001

            Bug ID: 37001
           Summary: [LLVM-COV] a pointer assignment after the return
                    statement is wrongly marked as executed in llvm-cov
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          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 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
int a = 0;
int e() {
  if (a) {
    int f;
    return 0;
    int *g = &f;
  } else {
    return 1;
  }
}
void main() {
  for (; a <= 3; a++)
    e();
}

$ 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 a = 0;
    2|      4|int e() {
    3|      4|  if (a) {
    4|      3|    int f;
    5|      3|    return 0;
    6|      3|    int *g = &f;
    7|      1|  } else {
    8|      1|    return 1;
    9|      1|  }
   10|      4|}
   11|      1|void main() {
   12|      5|  for (; a <= 3; a++)
   13|      4|    e();
   14|      1|}

Line #3 is marked as executed 3 times. However, this statement should be never
executed since it is after the return statement.

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