[Bug gcov-profile/93726] New: [GCOV] unexecuted functions lead to incorrect code coverage when it calls a function with a variable argument

[yangyibiao at hust dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93726

            Bug ID: 93726
           Summary: [GCOV] unexecuted functions lead to incorrect code
                    coverage when it calls a function with a variable
                    argument
           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
#include <stdarg.h>

long x, y;

inline void __attribute__((always_inline)) f1(va_list ap)
{
  x = va_arg(ap, double);
  x += va_arg(ap, long);
  x += va_arg(ap, double);
}

void foo(int i, ...)
{
  va_list ap;
  va_start(ap, i);
  f1(ap);
  va_end(ap);
}

void bar(int i, ...)
{
  va_list ap;
  va_start(ap, i);
  switch (i)
  {
  case 0:
    y = va_arg(ap, double);
    break;
  default:
    break;
  }
  f1(ap);
  va_end(ap);
}

void main(void) { foo(3, 16.0); }


$ gcc -O0 --coverage small.c; ./a.out; gcov small.c; cat small.c.gcov
File 'small.c'
Lines executed:42.11% of 19
Creating 'small.c.gcov'

    -:    0:Source:small.c
    -:    0:Graph:small.gcno
    -:    0:Data:small.gcda
    -:    0:Runs:1
    -:    1:#include <stdarg.h>
    -:    2:
    -:    3:long x, y;
    -:    4:
    -:    5:inline void __attribute__((always_inline)) f1(va_list ap)
    -:    6:{
#####:    7:  x = va_arg(ap, double);
    1*:    8:  x += va_arg(ap, long);
    1*:    9:  x += va_arg(ap, double);
    1*:   10:}
    -:   11:
    1:   12:void foo(int i, ...)
    -:   13:{
    -:   14:  va_list ap;
    1:   15:  va_start(ap, i);
    -:   16:  f1(ap);
    1:   17:  va_end(ap);
    1:   18:}
    -:   19:
#####:   20:void bar(int i, ...)
    -:   21:{
    -:   22:  va_list ap;
#####:   23:  va_start(ap, i);
#####:   24:  switch (i)
    -:   25:  {
#####:   26:  case 0:
#####:   27:    y = va_arg(ap, double);
#####:   28:    break;
#####:   29:  default:
#####:   30:    break;
    -:   31:  }
    -:   32:  f1(ap);
#####:   33:  va_end(ap);
#####:   34:}
    -:   35:
    1:   36:void main(void) { foo(3, 16.0); }


################################################################################
### We can find that: Line #7 is not executed.
### when the definition of function "bar" is removed from the source code, the
coverage will be different.
################################################################################