PATCH: flag_external and DECL_EXTERNAL documentation

[David Korn]

>-----Original Message-----
>From: Jason Merrill [ mailto:jason@redhat.com ]
>Sent: 02 February 2001 01:10


>> In the back end I'm currently writing, whenever a function call is to
>> be generated I need to know whether the function is defined in the
>> current translation unit or not.  After reading the comment, 
>I thought
>> DECL_EXTERNAL provided that information.
>
>> Since DECL_EXTERNAL doesn't quite work for this, is there another way
>> to find out whether a function is defined in the current translation
>> unit?  I'm assuming that the user may have to explicitly declare this
>> (i.e. declaring a function to be "extern", or not, in C).
>
>The rs6000 port uses
>
>  ((TREE_ASM_WRITTEN || !TREE_PUBLIC) && ! DECL_WEAK).

  ...to set the SYMBOL_REF_FLAG, by any chance ?  There's a couple of
catches with that that I've discovered.  One is that TREE_ASM_WRITTEN isn't
set until the final pass begins outputting assembler, so this will only spot
public (global) functions, and not (what would be described in C as) 
module static functions.  You might like to search the archives for a 
thread or two with "tests TREE_ASM_WRITTEN too early" in the subject line;
deciding that a function exists in the current translation unit turns out to
be quite tricky.

      DaveK
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