[Bug gcov-profile/90023] New: The coverage of a label is incorrect when it is after a return statement and followed by a blank statement

[yangyibiao at nju dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90023

            Bug ID: 90023
           Summary: The coverage of a label is incorrect when it is after
                    a return statement and followed by a blank 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
#include <stdio.h>

int foo(int a)
{
  void *l = &&error;

  if(a == 4)
    ; //goto *l;

  return 150;

error:
;//  return a;
}

int main(int argc, char **argv)
{
  printf("value: %d\n", foo(argc));

  return 0;
}

$ gcc -w --coverage small.c; ./a.out; gcov-8 small.c; cat small.c.gcov 
value: 150
File 'small.c'
Lines executed:100.00% 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:#include <stdio.h>
        -:    2:
        1:    3:int foo(int a)
        -:    4:{
        1:    5:  void *l = &&error;
        -:    6:
        -:    7:  if(a == 4)
        -:    8:    ; //goto *l;
        -:    9:
        2:   10:  return 150;
        -:   11:
        1:   12:error:
        -:   13:;//  return a;
        -:   14:}
        -:   15:
        1:   16:int main(int argc, char **argv)
        -:   17:{
        1:   18:  printf("value: %d\n", foo(argc));
        -:   19:
        1:   20:  return 0;
        -:   21:}

Line #12 is wrongly marked as executed and Line #10 is wrongly marked as
executed twice. 

When, Line #8 and Line #13 are not commented, the coverage is correct as:

        -:    0:Source:small.c
        -:    0:Graph:small.gcno
        -:    0:Data:small.gcda
        -:    0:Runs:1
        -:    0:Programs:1
        -:    1:#include <stdio.h>
        -:    2:
        1:    3:int foo(int a)
        -:    4:{
        1:    5:  void *l = &&error;
        -:    6:
        1:    7:  if(a == 4)
    #####:    8:    goto *l;
        -:    9:
        1:   10:  return 150;
        -:   11:
    #####:   12:error:
    #####:   13:  return a;
        -:   14:}
        -:   15:
        1:   16:int main(int argc, char **argv)
        -:   17:{
        1:   18:  printf("value: %d\n", foo(argc));
        -:   19:
        1:   20:  return 0;
        -:   21:}