calling setjmp destruct a variable

[Takakazu Satoh]

In Ubuntu 18.04 armhf with gcc-7, the following code, which compiles normally, gives incorrect result (on my machine, -964176505 instead of correct value 1).

#include <setjmp.h>
#include <stdio.h>

jmp_buf a[10] ;
jmp_buf * volatile sp = a ;

int main()
{
    if (setjmp(*sp++) == 0) {
 printf("diff=%td\n", sp-a) ;
 return 0 ;
    }
    return 1 ;
}

Additional information:
The above code gives correct answer on Ubuntu 16.04 x86_64 gcc 5.4.
If I replace '*sp++' with '*++sp', the program gives correct value 1.

[Takakazu Satoh (takakazu)]

The command 'apt-get upgrade' upgraded gcc-7 from 7.3.0-27ubuntu1~18.04 to 7.4.0-1ubuntu1~18.04.
However, this bug still exists in gcc 7.4.0.

By the way, I found that a slightly simple code give rise to an internal compiler error as follows.

$ cat << EOF > foo.c
#include <setjmp.h>
#include <stdio.h>

jmp_buf a[10] ;
jmp_buf * volatile sp = a ;

int main()
{
    setjmp(*sp++) ;
    printf("diff=%td\n", sp-a) ;
}
EOF

$ gcc foo.c
foo.c: In function 'main':
foo.c:9:5: internal compiler error: Segmentation fault
     setjmp(*sp++) ;
     ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions.