[Bug gcov-profile/93766] New: [GCOV] incorrect coverage when compiled with option '-fsanitize=undefined' for struct assignment statement

[yangyibiao at hust dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93766

            Bug ID: 93766
           Summary: [GCOV] incorrect coverage when compiled with option
                    '-fsanitize=undefined' for struct assignment statement
           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 <string.h>

typedef struct 
{
  int e;
} S;

inline __attribute__ ((always_inline)) void foo (S *y)
{
  S c = *y;
}

void main (void)
{
  S y;
  memset (&y, 0, sizeof (y));
  foo(&y);
}

$ gcc -O0 --coverage -fsanitize=undefined small.c; ./a.out; gcov 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
        -:    1:#include <string.h>
        -:    2:
        -:    3:typedef struct 
        -:    4:{
        -:    5:  int e;
        -:    6:} S;
        -:    7:
        -:    8:inline __attribute__ ((always_inline)) void foo (S *y)
        -:    9:{
        2:   10:  S c = *y;
        1:   11:}
        -:   12:
        1:   13:void main (void)
        -:   14:{
        -:   15:  S y;
        1:   16:  memset (&y, 0, sizeof (y));
        -:   17:  foo(&y);
        1:   18:}


####################################################
We can find that Line #10 is wrongly marked as executed twice. 
When compiling without "-fsanitize=undefined", the coverage will be correct.