[Bug c/89909] New: false positive for for -Wunreachable-code.

[pawel_sikora at zoho dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89909

            Bug ID: 89909
           Summary: false positive for for -Wunreachable-code.
           Product: gcc
           Version: 8.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pawel_sikora at zoho dot com
  Target Milestone: ---

#include <cstdio>

void foo( int i ) {
    char const* j = nullptr;

    switch ( i ) {

        if ( 0 ) {
        case 1:
            j = "one";
        }
        if ( 0 ) {
        case 2:
            j = "two";
        }
        {
            std::printf( "%s\n", j );
            return;
        }

        default:
            std::puts( "unknown" );
    };
}

int main() {
    foo( 0 );
    foo( 1 );
    foo( 2 );
    foo( 3 );
    return 0;
}


// g++ (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2)
% g++ t.cpp -Wall -Wunreachable-code -o t && ./t                                
t.cpp: In function ‘void foo(int)’:
t.cpp:8:9: warning: statement will never be executed [-Wswitch-unreachable]
         if ( 0 ) {
         ^~
unknown
one
two
unknown