[llvm-bugs] [Bug 49439] New: [LLVM-COV] "return" statement and "exit" statement lead to incorrect coverage

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49439

            Bug ID: 49439
           Summary: [LLVM-COV]    "return" statement and "exit" statement
                    lead to incorrect coverage
           Product: Runtime Libraries
           Version: 11.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          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>
unsigned test(unsigned one, unsigned bit) {
  unsigned val = bit & 1;
  unsigned zero = one >> 1;

  val++;
  return zero + (val >> 1);
}

int main() {
  if (test(1, 0) != 0)
    abort();
  if (test(1, 1) != 1)
    abort();
  if (test(1, 65535) != 1)
    abort();
  printf("0\n");
  exit(0);
  printf("1\n");
  return 0;
  printf("2\n");
  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
0
    1|       |#include<stdio.h>
    2|      3|unsigned test(unsigned one, unsigned bit) {
    3|      3|  unsigned val = bit & 1;
    4|      3|  unsigned zero = one >> 1;
    5|      3|
    6|      3|  val++;
    7|      3|  return zero + (val >> 1);
    8|      3|}
    9|       |
   10|      1|int main() {
   11|      1|  if (test(1, 0) != 0)
   12|      0|    abort();
   13|      1|  if (test(1, 1) != 1)
   14|      0|    abort();
   15|      1|  if (test(1, 65535) != 1)
   16|      0|    abort();
   17|      1|  printf("0\n");
   18|      1|  exit(0);
   19|      1|  printf("1\n");
   20|      0|  return 0;
   21|      1|  printf("2\n");
   22|      0|  return 0;
   23|      1|}

Only line 17 was executed among the three "printf" statements. Line #19 and #21
were wrongly marked as executed.

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