[Bug gcov-profile/93680] New: [GCOV] "do-while" structure in case statement leads to incorrect code coverage

[yangyibiao at hust dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93680

            Bug ID: 93680
           Summary: [GCOV] "do-while" structure in case statement leads to
                    incorrect code coverage
           Product: gcc
           Version: 9.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yangyibiao at hust dot edu.cn
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

$ gcov -v
gcov (GCC) 9.2.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or 
FITNESS FOR A PARTICULAR PURPOSE.


$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --enable-shared
--enable-threads=posix --with-system-zlib --with-isl --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch
--disable-libssp --enable-gnu-unique-object --enable-linker-build-id
--enable-lto --enable-plugin --enable-install-libiberty
--with-linker-hash-style=gnu --enable-gnu-indirect-function --enable-multilib
--disable-werror --enable-checking=release --enable-default-pie
--enable-default-ssp --enable-cet=auto gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
gcc version 9.2.0 (GCC)


$ cat small.c
int f(int s, int n)
{
  int p = 0;

  switch (s)
  {
    case 0:
        do { p++; } while (--n);
        return p;

    case 1:
        do { p++; } while (--n);
        return p;
  }

  return 0;
}

void main() { f(0, 5); f(1, 5); }

$ gcc -O0 --coverage small.c; ./a.out; gcov small.c; cat small.c.gcov
File 'small.c'
Lines executed:90.91% of 11
Creating 'small.c.gcov'

    -:    0:Source:small.c
    -:    0:Graph:small.gcno
    -:    0:Data:small.gcda
    -:    0:Runs:1
    2:    1:int f(int s, int n)
    -:    2:{
    2:    3:  int p = 0;
    -:    4:
    2:    5:  switch (s)
    -:    6:  {
    5:    7:    case 0:
    5:    8:        do { p++; } while (--n);
    1:    9:        return p;
    -:   10:
    4:   11:    case 1:
    5:   12:        do { p++; } while (--n);
    1:   13:        return p;
    -:   14:  }
    -:   15:
#####:   16:  return 0;
    -:   17:}
    -:   18:
    1:   19:void main() { f(0, 5); f(1, 5); }



###############################################################################
### We can find that: Line #7 is executed 5 times, Line #11 is executed 4
times.
### In my opinion, both of these two statements (Line #7 and Line #11) should
only executed once. 
### OR AT LEAST, they should with same coverage statistics: both executed are 4
or 5 times.
### When we replace the "do-while" statement to "while" structure, the coverage
is correct
###############################################################################