[Bug gcov-profile/90057] New: [GCOV] Wrong coverage for "if()" statement while it is embedded with an empty "for(;0;)" loop statement

[yangyibiao at nju dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90057

            Bug ID: 90057
           Summary: [GCOV] Wrong coverage for "if()" statement while it is
                    embedded with an empty "for(;0;)" loop statement
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yangyibiao at nju dot edu.cn
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/8/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
8.2.0-1ubuntu2~18.04' --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-8
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie
--with-system-zlib --with-target-system-zlib --enable-objc-gc=auto
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 8.2.0 (Ubuntu 8.2.0-1ubuntu2~18.04)

$ cat small.c

int main()
{
  int b = 0, d = 0, f = 0, p = -1;

  if (f > p && p)
    for (; 0;)
       ;
  else if (d)
    b = 0 >= b;

  return 0;
}

$ gcc -w -O0 --coverage small.c; ./a.out; gcov-8 small.c; cat small.c.gcov
File 'small.c'
Lines executed:71.43% of 7
Creating 'small.c.gcov'

        -:    0:Source:small.c
        -:    0:Graph:small.gcno
        -:    0:Data:small.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        -:    1:
        1:    2:int main()
        -:    3:{
        1:    4:  int b = 0, d = 0, f = 0, p = -1;
        -:    5:
        2:    6:  if (f > p && p)
        1:    7:    for (; 0;)
        -:    8:       ;
    #####:    9:  else if (d)
    #####:   10:    b = 0 >= b;
        -:   11:
        1:   12:  return 0;
        -:   13:}

Line #6 is wrongly marked as executed twice. 

While Line 7 is removed. The result is correct as:
$ gcc -w -O0 --coverage small.c; ./a.out; gcov-8 small.c; cat small.c.gcov
File 'small.c'
Lines executed:66.67% of 6
Creating 'small.c.gcov'

        -:    0:Source:small.c
        -:    0:Graph:small.gcno
        -:    0:Data:small.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        -:    1:
        1:    2:int main()
        -:    3:{
        1:    4:  int b = 0, d = 0, f = 0, p = -1;
        -:    5:
        1:    6:  if (f > p && p)
        -:    7:    // for (; 0;)
        -:    8:       ;
    #####:    9:  else if (d)
    #####:   10:    b = 0 >= b;
        -:   11:
        1:   12:  return 0;
        -:   13:}

While Line #9 and Line #10 are both removed, the result is also correct as:
$ gcc -w -O0 --coverage small.c; ./a.out; gcov-8 small.c; cat small.c.gcov
File 'small.c'
Lines executed:100.00% of 5
Creating 'small.c.gcov'

        -:    0:Source:small.c
        -:    0:Graph:small.gcno
        -:    0:Data:small.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        -:    1:
        1:    2:int main()
        -:    3:{
        1:    4:  int b = 0, d = 0, f = 0, p = -1;
        -:    5:
        1:    6:  if (f > p && p)
        1:    7:    for (; 0;)
        -:    8:       ;
        -:    9:  // else if (d)
        -:   10:  //   b = 0 >= b;
        -:   11:
        1:   12:  return 0;
        -:   13:}