PCC param processing: the whole sorid story. storage class checks

[Steve Serocki]

Subject: PCC's Indefensible Argument Processing -- storage class checks
Index:  lib/mip/pftn.c 4.2BSD

Description:
	Error checking in the portable C compiler's semantic analysis
	phase has always been less than rigorous, to the point now of
	being the butt of cruel jokes comparing the pcc in robustness
	to the C shell.  Recent ridicule (*) has been directed
	especially at the comic handling of irregular parameter 
	declarations.

	The pcc will often respond to missing parameters with a "bad
	arg temp" warning, and then go on to generate incorrect code.
	a catch for the "bad arg temp" bug is described in a second,
	co-posted bug report.

	The pcc will disdain catching parameters described as "static",
	or "extern" storage class in semantic analysis, ultimately
	falling on its nose in codegen, or, gosh forbid, at assemble
	time or later if other bugs are present.  A catch for the
	misspecified parameter SC is described here.  The problem 
	is simply that the appropriate check against these two 
	meaningless storage classes is never made.

	[(*) Refs: 3015 at utah-cs.UUCP, 8180-8181 at ucmp-cs.UUCP]


Repeat-By:
	Give the following C program to the pcc.  The compilation will
	terminate ungracefully with an internal compiler error.

	main(perverse )
		static int perverse;	/* bad storage class */
	{
	}


Fix:
	A formal parameter SC may be only PARAM (undeclared, implicit)
	or REGISTER.  [ See K&R, appendix A, on external function defs]
	It seems reasonable to catch misdeclarations of parameter SC 
	in fixclass().  One way to do this is shown in the context diff 
	below.

*** pftn.c	Sun Jul 17 13:37:05 1983
--- jess.pftn.c	Tue Sep  4 04:09:07 1984
***************
*** 1562,1567
  		else class = AUTO;
  
  		}
  
  	/* now, do general checking */
  

--- 1562,1574 -----
  		else class = AUTO;
  
  		}
+ #ifdef STONEWALL
+ 	else if( blevel == 1 && class != PARAM && class != REGISTER) {
+ 		uerror( "declared parameter has illegal storage class" );
+ 		return( PARAM);
+ 		}
+ #endif
+ 		
  
  	/* now, do general checking */