Return Statement Reachability

[redbow-kimee]

Possibly related to #10

Go enforces a syntactic reachability analysis for returns, while C never required that returns be reachable and C compilers which do reachability use more sophisticated algorighms. Some situations where the return statement is considered reachable (or at least not an issue) by C are not considered reachable by Go.

It appears that cxgo has implemented a bit of checking to implicitly add missing returns (see postproc.go:fixImplicitReturnStmts). However, I've found a test case which is improperly handled.

#include <stdio.h>

#define TRUE 1
#define FALSE 0

int implicit_return(char* str)
{
    while(TRUE)
    {
        while(TRUE)
        {
            if(*str == '\0') { return 0; }
            else if(*str != 'a') { break; }
            str++;
        }

        printf("%c is not a\n", *str);
        str++;
    }
}

int main()
{
    return implicit_return("aaabaababaaaaa");
}

I believe the last line of this function should have an (actually unreachable) return 0 added to fool Go into believing there is a reachable return 0.

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[dennwc]

Thank you for providing a reproducer, I will check why reachability analysis fails for this case.