[cfe-dev] #pragma weak handling

[Erik Cederstrand]

Den 25/11/2009 kl. 23.19 skrev Abramo Bagnara:

> struct in6_addr
>   {
>     union
>       {
>         unsigned char __u6_addr8[16];
>         unsigned short __u6_addr16[8];
>         unsigned int __u6_addr32[4];
>     } __in6_u;
> };
> 
> extern const struct in6_addr in6addr_any;
> 
> static const struct in6_addr local_in6addr_any = { { { 
> 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 } } };
> #pragma weak in6addr_any = local_in6addr_any
> 
> Examining the ast generated for this snippet I note two problems:
> 
> 1) the extra declaration generated by #pragma has the following form:
> 
> static const struct in6_addr in6addr_any __attribute__ ((weak)) 
> __attribute__ ((alias("local_in6addr_any")));
> 
> The problem I see is that "static" should be replaced by "extern".
> 
> I think that the bug is in Sema::DeclClonePragmaWeak(NamedDecl *ND, 
> IdentifierInfo *II) where it is copied also the storage class of VarDecl.
> 
> 2) the extra declaration generated by #pragma seems to be not linked to 
> other declarations for the same object and then getCanonicalDecl does 
> not work as expected.
> 
> I'd like to know if this analysis is correct and if yes, what's the 
> suggested way to fix point 2 (I think that the fix to point 1 is rather 
> obvious).

Bug #3679 covers this problem, I think. Comment #32 states that "#pragma weak foo" after defining function foo() doesn't work.

Thanks,
Erik Cederstrand
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