[llvm-bugs] [Bug 51270] New: [LLVM-COV] Wrong coverage after a "for" loop.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=51270

            Bug ID: 51270
           Summary: [LLVM-COV] Wrong coverage after a "for" loop.
           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 <assert.h>
#include <stdio.h>
#include <string.h>

#define SIZE 1000
int t0 = 0;
const char *t2[SIZE];
char buf[SIZE];

void foo(void) {
  char *s = buf;
  t0 = 1;

  for (;;) {
    if (*s == '\0')
      break;
    else {
      t2[t0] = s;
      t0++;
    }
    *s++ = '\0';
  }
  t2[t0] = NULL;
}

int main() {
  strcpy(buf, "hello");
  foo();
  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 <assert.h>
    2|       |#include <stdio.h>
    3|       |#include <string.h>
    4|       |
    5|       |#define SIZE 1000
    6|       |int t0 = 0;
    7|       |const char *t2[SIZE];
    8|       |char buf[SIZE];
    9|       |
   10|      1|void foo(void) {
   11|      1|  char *s = buf;
   12|      1|  t0 = 1;
   13|      1|
   14|      6|  for (;;) {
   15|      6|    if (*s == '\0')
   16|      1|      break;
   17|      5|    else {
   18|      5|      t2[t0] = s;
   19|      5|      t0++;
   20|      5|    }
   21|      6|    *s++ = '\0';
   22|      5|  }
   23|      1|  t2[t0] = NULL;
   24|      1|}
   25|       |
   26|      1|int main() {
   27|      1|  strcpy(buf, "hello");
   28|      1|  foo();
   29|      1|  return 0;
   30|      1|}

Line 21 should only be executed 5 times.

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