[PATCH] fold: Fix up strn{case,}cmp folding [PR98771]

[Jakub Jelinek]

On Sun, Jan 31, 2021 at 01:49:29PM +0100, Eric Botcazou wrote:
> > The important difference is for strn{,case}cmp folding, we pass that s2
> > value as the last argument to the host functions comparing the c_getstr
> > results.  If s2 fits into size_t, then my patch makes no difference,
> > but if it is larger, we know the 2 c_getstr objects need to fit into the
> > host address space, so larger s2 should just act essentially as strcmp
> > or strcasecmp; as none of those objects can occupy 100% of the address
> > space, using MIN (SIZE_MAX, s2) achieves that.
> 
> But SIZE_MAX is a host value, isn't it?  As a matter of fact, it breaks the 

Sure.

> build with somewhat ancient glibcs:
> 
> In file included from ../../src/gcc/fold-const-call.c:21:
> 
> ../../src/gcc/fold-const-call.c: In function 'tree_node* 
> fold_const_call(combined_fn, tree, tree, tree, tree)':
> 
> ../../src/gcc/fold-const-call.c:1777:56: error: 'SIZE_MAX' was not declared in 
> this scope
> 
>  1777 |  return build_int_cst (type, strncmp (p0, p1, MIN (s2, SIZE_MAX)));
> 
> because /usr/include/stdint.h has:
> 
> /* The ISO C99 standard specifies that in C++ implementations these
>    macros should only be defined if explicitly requested.  */
> #if !defined __cplusplus || defined __STDC_LIMIT_MACROS

Ugh.  Anyway, we don't really need the SIZE_MAX macro, we can use
INTTYPE_MAXIMUM (size_t) or (~(size_t) 0) too instead of it.

	Jakub