SIGSEGV in dfa.cpp for alpha 0.3.1

[Anonymous]

I've compiled alpha 0.3.1 on my Linux server. I've updated my CVS working copy as of a few moments ago. Looks like there haven't been any recent changes.

I have revision 1.74 of dfa.cpp and the reason for the SIGSEGV is an attempt to dereference a null pointer in the case when the op is opGlobal:

1200: void Unary::descendType(Type* parentType, bool& ch, Statement* s){
1201:     switch (op) {
...
1261:         case opGlobal: {
1262:             Prog* prog = s->getProc()->getProg();
1263:             char* name = ((Const*)subExp1)->getStr();
1264:             Type* ty = prog->getGlobalType(name);
1265:             ty = ty->meetWith(parentType, ch);
1266:             prog->setGlobalType(name, ty);
1267:             break;
1268:         }
...

prog->getGlobalType(name) returns a null pointer for the given input and, of course, the SIGSEGV is thrown on line 1265 when it is dereferenced.

I'd <em>love</em> to code the fix but since I am totally unfamiliar with Unary::decendType I thought it would be wise to ask first if anyone has a good suggestion.

I could try executing lines 1265 and 1266 only if ty is not null but I would not know if the output is valid.

Thanks for any assistance you can render.
Jeff

[Andy Bach]

Hmm, there this:
          Type *ty = prog->getGlobalType((char*)gloName);
                 if (s->isAssign() && ((Assign*)s)->getType()) {
                   int bits = ((Assign*)s)->getType()->getSize();
                   if (ty == NULL || ty->getSize() == 0)
                     prog->setGlobalType((char*)gloName, new IntegerType(bits));
                 }

around line 200 in dfa. I tried:
   case opGlobal: {
         Prog* prog = s->getProc()->getProg();
         char* name = ((Const*)subExp1)->getStr();
         Type* ty = prog->getGlobalType(name);
         if (ty == NULL || ty->getSize() == 0) {
              prog->setGlobalType(name, new IntegerType(1));
              // prog->setGlobalType((char*)gloName, new IntegerType(bits));
         } else {
           ty = ty->meetWith(parentType, ch);
           prog->setGlobalType(name, ty);
         }
         break;

but w/ the same result.