[patch] Improve comments and INITFINI macro use in vxcrtsutff.c

[Olivier Hainque <hainque@adacore.com>]

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Hello,

This change augments the comment attached to the use of auto-host.h
in vxcrtstuff.c to better describe the reason for including it and
for the associated series of #undef directives.

It also augments the comment on dso_handle and removes a redundant
guard on HAVE_INITFINI_ARRAY_SUPPORT for the shared version of the
objects, nested within a section guarded on USE_INITFINI_ARRAY.

We have been using this for a while in gcc-11 based production
toolchains and I have performed a few build+test sanity checks with
gcc-12 for powerpc64-vxworks7r2. This is supposedly a noop.

Will commit to mainline shortly.

Olivier

2022-03-06  Olivier Hainque  <hainque@adacore.com>

libgcc/
        * config/vxcrtstuff.c: Improve the comment attached to the use
        of auto-host.h and of __dso_handle.  Remove redundant guard on
        HAVE_INITFINI_ARRAY_SUPPORT within a USE_INITFINI_ARRAY section.


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From 4ecad9c409c09f6108bbaaff1ee8805a076c45a6 Mon Sep 17 00:00:00 2001
From: Olivier Hainque <hainque@adacore.com>
Date: Mon, 7 Mar 2022 11:50:27 +0000
Subject: [PATCH 17/18] Improve comments and INITFINI macro use in vxcrtsutff.c

This change augments the comment attached to the use of auto-host.h
in vxcrtstuff.c to better describe the reason for including it and
for the associated series of #undef directives.

It also augments the comment on dso_handle and removes a redundant
guard on HAVE_INITFINI_ARRAY_SUPPORT for the shared version of the
objects, nested within a section guarded on USE_INITFINI_ARRAY.

2022-03-06  Olivier Hainque  <hainque@adacore.com>

libgcc/
	* config/vxcrtstuff.c: Improve the comment attached to the use
	of auto-host.h and of __dso_handle.  Remove redundant guard on
	HAVE_INITFINI_ARRAY_SUPPORT within a USE_INITFINI_ARRAY section.
---
 libgcc/config/vxcrtstuff.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/libgcc/config/vxcrtstuff.c b/libgcc/config/vxcrtstuff.c
index 80f51f7399d..5045acfc6da 100644
--- a/libgcc/config/vxcrtstuff.c
+++ b/libgcc/config/vxcrtstuff.c
@@ -26,15 +26,21 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #define IN_LIBGCC2
 
-/* FIXME: Including auto-host is incorrect, but until we have
-   identified the set of defines that need to go into auto-target.h,
-   this will have to do.  */
+/* FIXME: Including auto-host is incorrect here (target library implementation
+   file), but we still need it for DEFAULT_USE_CXA_ATEXIT and most importantly
+   USE_INITFINI_ARRAY, guarded by HAVE_INITFINI_ARRAY_SUPPORT, not yet handled
+   by auto-target.h.  Proceed as crtstuff.c, with the inclusion followed by a
+   few #undefs preventing build failures in configurations setup for Windows
+   hosts, including canadian builds.  #define USED_FOR_TARGET would circumvent
+   this but would unfortunately also inhibit some of the definitions we
+   need.  */
 #include "auto-host.h"
 #undef caddr_t
 #undef pid_t
 #undef rlim_t
 #undef ssize_t
 #undef vfork
+
 #include "tconfig.h"
 #include "tsystem.h"
 #include "coretypes.h"
@@ -58,17 +64,19 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #ifdef CRT_BEGIN
 
+/* Provide __dso_handle in RTP objects, which might be included in contexts
+   involving shared objects.  This mimics the crtstuff.c behavior:  dso_handle
+   should be NULL for the main program (in vx_crtbegin.o) and a unique value
+   for the shared libraries (in vx_crtbeginS.o).  */
+
 #if DEFAULT_USE_CXA_ATEXIT && defined(__RTP__)
-/* This mimics the crtstuff.c behavior.  dso_handle should be NULL for the
-   main program (in vx_crtbegin.o) and a unique value for the shared libraries
-   (in vx_crtbeginS.o).   */
 extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
 #ifdef CRTSTUFFS_O
 void *__dso_handle = &__dso_handle;
 #else
 void *__dso_handle = 0;
 #endif
-#endif /* DEFAULT_USE_CXA_ATEXIT */
+#endif
 
 /* Determine what names to use for the constructor/destructor functions.  */
 
@@ -103,7 +111,7 @@ void *__dso_handle = 0;
    where we don't want to drag libc_internal contents blindly and which
    provides functions with a slightly different name anyway.  */
 
-#if HAVE_INITFINI_ARRAY_SUPPORT && defined(CRTSTUFFS_O)
+#if defined(CRTSTUFFS_O)
 
 /* Run through the .init_array, .fini_array sections.  The linker script
    *must* provide __init_array_start, __init_array_end, __fini_array_start,
-- 
2.25.1