Re: [PATCH] hurd: Add shared mig declarations

[Simon Marchi <simark@simark.ca>]

On 2020-05-30 2:23 p.m., Samuel Thibault wrote:
> Fixes
> 
> exc_request_S.c:177:24: error: no previous declaration for ‘exc_server’ [-Werror=missing-declarations]
>   177 | mig_external boolean_t exc_server
> 
> gdb/ChangeLog:
> 
> 	* config/i386/i386gnu.mn [%_S.o %_U.o] (COMPILE.post): Add
> 	"-include gnu-nat-mig.h".
> 	* gnu-nat-mig.h: New file.
> 	* gnu-nat.c: Include "gnu-nat-mig.h".
> 	(exc_server, msg_reply_server, notify_server,
> 	process_reply_server): Remove declarations.

It took me a while to understand the underlying problem.  My understanding is that
gnu-nat.c calls this function exc_server, that is defined in the generated file.  The
generated file does not provide a header with declarations, so gnu-nat.c had its own
local declaration.  Since we now use the -Wmissing-declarations warning flag, and the
definition in the generated exc_request_S.c didn't see a corresponding declaration,
it caused that build failure.  Is that correct?  If so, please add that explanation
or equivalent to the commit log.

My question now is: that MIG tool appears to generate both a header (%_S.h) and source
file (%_S.c) from defs files.  What is this header file used for, if it doesn't contain
the declaration for the functions in the source file?

Simon