RFC: Stricter semantics for renaming pragmas

[Ian Lance Taylor]

Zack Weinberg <zack@codesourcery.com> writes:

> 1) If any of the three ways of changing DECL_ASSEMBLER_NAME is applied
>    to a decl whose DECL_ASSEMBLER_NAME is already set, a warning
>    issues and the name does not change.  (The warning does not issue
>    if it's a redundant operation - only if it's inconsistent.)

Sounds reasonable.

> 2) If #pragma extern_prefix is in effect and a declaration occurs with
>    an __asm__ name, __asm__ wins.  No warning issues.

Sounds reasonable (and is an exception to case 1 in that no warning is
issued).

> 3) If #pragma extern_prefix is in effect, all pending #pragma
>    redefine_extname operations are ignored; a warning does issue.

Sounds reasonable (and is implied by case 1).  Since the two #pragmas
exist to support the system header files on two different systems, I
don't think the semantics of using both of them together are very
important.

> 4) The "source name" for #pragma redefine_extname is the DECL_NAME,
>    *not* the DECL_ASSEMBLER_NAME.  (Current code is inconsistent -
>    it's the DECL_NAME if the #pragma occurs after the declaration, the
>    DECL_ASSEMBLER_NAME if the #pragma occurs before the declaration.

The #pragma is supposed to appear in the source code before the
declaration.  It shouldn't be applied to declarations which appear
before the #pragma.  I may misunderstand what you are saying.
Applying to the DECL_NAME sounds right in any case.

> 5) In C++:
> 
> 5a) Applying __asm__("name") to a declaration silently makes it extern "C".

Sounds right--that doesn't change the calling convention in any way,
right?  It just changes the name.

> 5b) #pragma redefine_extname is ignored, with a warning, if applied to
>     a declaration which is not extern "C".

I don't think this is right.  I think that this usage of #pragma
redefine_extname ought to be like applying __asm__("name")--it should
change the declaration to effectively be extern "C".

> 5c) #pragma extern_prefix silently applies only to declarations which
>     are extern "C".

I don't think this is right either.  I think that it should apply to
all external names, or at the very least it should issue a warning.

Ian