[Bug c/83736] New: ICE triggered by improper use of VLA and scanf

[czirkos.zoltan at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83736

            Bug ID: 83736
           Summary: ICE triggered by improper use of VLA and scanf
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: czirkos.zoltan at gmail dot com
  Target Milestone: ---

Created attachment 43059
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43059&action=edit
Compiler output

The following code causes an internal compiler error and segmentation fault in
the compiler:

#include <stdio.h>

int main(void){
    int n = 0;
    char temp[n + 1];
    scanf("%s", &temp);
}

Of course the code is invalid (the address-of operator is not needed), but it
should not cause an ICE.

Attached compiler output.

Version is "gcc version 7.0.1 20170407 (experimental) [trunk revision 246759]
(Ubuntu 7-20170407-0ubuntu2)".
Command line is "gcc test.c".

The compiler also crashes if the call is not scanf but printf. And it also
crashes when all warnings are turned off (gcc -w).