[llvm-bugs] [Bug 41849] New: [[LLVM-COV] #if #endif in the source code lead to incorrect coverage report when exit() statement follows "while() ; "

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41849

            Bug ID: 41849
           Summary: [[LLVM-COV] #if #endif in the source code lead to
                    incorrect coverage report when exit() statement
                    follows "while() ;"
           Product: Runtime Libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: libprofile library
          Assignee: unassignedbugs at nondot.org
          Reporter: yangyibiao at nju.edu.cn
                CC: llvm-bugs at lists.llvm.org

$ clang -v
clang version 9.0.0-svn358899-1~exp1+0~20190422164136.937~1.gbpac4d8e (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/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.5.0
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/7.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
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/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64


$ cat small.c
extern void abort (void);
extern void exit (int);

int
main (void)
{
#if __INT_MAX__ >= 2147483647
  struct { int count: 31; } s = { 0 };
  while (s.count--)
    ; // abort ();
#elif __INT_MAX__ >= 32767
  abort(1);
#else
#endif
  exit (2);
}



$ clang -w -O0 -g -fcoverage-mapping -fprofile-instr-generate=small.profraw
small.c; ./a.out; echo $?; 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
2
    1|       |extern void abort (void);
    2|       |extern void exit (int);
    3|       |
    4|       |int
    5|       |main (void)
    6|      1|{
    7|      1|#if __INT_MAX__ >= 2147483647
    8|      1|  struct { int count: 31; } s = { 0 };
    9|      1|  while (s.count--)
   10|      0|    ; // abort ();
   11|       |#elif __INT_MAX__ >= 32767
   12|       |  abort(1);
   13|       |#else
   14|       |#endif
   15|       |  exit (2);
   16|      1|}

Line # 15 is marked as "" which indicates that it is not an instrumentation
site.
However, we can found that the exit code of this program is 2. Thus we can
determine that line #15 is executed during this execution. 

When Line #10 is not removed, Line #15 is marked as executed once as follows. 

$ clang -w -O0 -g -fcoverage-mapping -fprofile-instr-generate=small.profraw
small.c; ./a.out; echo $?; 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
2
    1|       |extern void abort (void);
    2|       |extern void exit (int);
    3|       |
    4|       |int
    5|       |main (void)
    6|      1|{
    7|      1|#if __INT_MAX__ >= 2147483647
    8|      1|  struct { int count: 31; } s = { 0 };
    9|      1|  while (s.count--)
   10|      0|    abort ();
   11|       |#elif __INT_MAX__ >= 32767
   12|       |  abort(1);
   13|       |#else
   14|       |#endif
   15|      1|  exit (2);
   16|      1|}

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