[Bug gcov-profile/85199] New: [GCOV] A cond-expr with a iterative variable in a for loop is marked as "-" in gcov

[yangyibiao at nju dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85199

            Bug ID: 85199
           Summary: [GCOV] A cond-expr with a iterative variable in a for
                    loop is marked as "-" in gcov
           Product: gcc
           Version: 8.0
            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 
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
8-20170923-1ubuntu2' --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs
--enable-languages=c,c++,go,brig,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 --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
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 8.0.0 20170923 (experimental) [trunk revision 253118] (Ubuntu
8-20170923-1ubuntu2)

$ cat small.c
void main()
{
    int b = 0;
    for(;
    b < 1;
    b++) {
        ;
    }
}

$ gcc -w --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:void main()
        -:    2:{
        1:    3:    int b = 0;
        2:    4:    for(;
        -:    5:    b < 1;
        1:    6:    b++) {
        -:    7:        ;
        -:    8:    }
        1:    9:}

Here, we can see that Line #4 is marked as executed twice and Line #5 "b < 1;"
is marked as "-".

I was wondering whether this is a bug. 

Since b is changed in each loop, such that "b < 1" should not be optimized out.
Therefore, I think the correct mark should be as follows: 
Line #4 is marked as executed once and Line #5 is marked as executed twice.