[PATCH] gcc/gcc.c: add outfiles spec

[Rasmus Villemoes]

Commit 0b7fb27b698d (Fix and document -r option) broke building of
VxWorks modules, at least for our version of VxWorks. A VxWorks module
is a relocatable ELF file - the final link is done when the file is
linked in to the running kernel. So building with -r is
necessary. However, the module also needs to be wrapped in
crtbegin.o/crtend.o in order to have the exception frame info
registered with the run-time.

We used to achieve that with a custom spec file that specified
crtbegin.o and crtend.o as start/endfile, but after the above commit,
%S and %E no longer get substituted.

In order to allow custom spec files to add arbitrary objects at the
beginning/end, add a level of indirection that puts "%o" in a new
outfiles spec - then the custom spec file can override that with the

%rename outfiles old_outfiles

*outfiles:
  ...

idiom.

Of course, the custom spec file could also override all of the
link_command, but that's a lot of logic to copy-paste and keep in
sync.

gcc/ChangeLog:

2020-04-04  Rasmus Villemoes  <rv@rasmusvillemoes.dk>

	* gcc.c (OUTFILES_SPEC): New spec, hook for wrapping or
          overriding %o.
	
---
I'm not quite up to speed on how the gcc repo works after the switch
to git. Please advise.

 gcc/gcc.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gcc/gcc.c b/gcc/gcc.c
index 9f790db0daf..7ea7e2a3ae0 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -804,6 +804,10 @@ proper position among the other output files.  */
 #define ENDFILE_SPEC ""
 #endif
 
+#ifndef OUTFILES_SPEC
+#define OUTFILES_SPEC "%o"
+#endif
+
 #ifndef LINKER_NAME
 #define LINKER_NAME "collect2"
 #endif
@@ -1042,7 +1046,7 @@ proper position among the other output files.  */
    "%X %{o*} %{e*} %{N} %{n} %{r}\
     %{s} %{t} %{u*} %{z} %{Z} %{!nostdlib:%{!r:%{!nostartfiles:%S}}} \
     %{static|no-pie|static-pie:} %@{L*} %(mfwrap) %(link_libgcc) " \
-    VTABLE_VERIFICATION_SPEC " " SANITIZER_EARLY_SPEC " %o "" \
+    VTABLE_VERIFICATION_SPEC " " SANITIZER_EARLY_SPEC " %(outfiles) "" \
     %{fopenacc|fopenmp|%:gt(%{ftree-parallelize-loops=*:%*} 1):\
 	%:include(libgomp.spec)%(link_gomp)}\
     %{fgnu-tm:%:include(libitm.spec)%(link_itm)}\
@@ -1087,6 +1091,7 @@ static const char *link_gomp_spec = "";
 static const char *libgcc_spec = LIBGCC_SPEC;
 static const char *endfile_spec = ENDFILE_SPEC;
 static const char *startfile_spec = STARTFILE_SPEC;
+static const char *outfiles_spec = OUTFILES_SPEC;
 static const char *linker_name_spec = LINKER_NAME;
 static const char *linker_plugin_file_spec = "";
 static const char *lto_wrapper_spec = "";
@@ -1596,6 +1601,7 @@ static struct spec_list static_specs[] =
   INIT_STATIC_SPEC ("linker_plugin_file",	&linker_plugin_file_spec),
   INIT_STATIC_SPEC ("lto_wrapper",		&lto_wrapper_spec),
   INIT_STATIC_SPEC ("lto_gcc",			&lto_gcc_spec),
+  INIT_STATIC_SPEC ("outfiles",			&outfiles_spec),
   INIT_STATIC_SPEC ("post_link",		&post_link_spec),
   INIT_STATIC_SPEC ("link_libgcc",		&link_libgcc_spec),
   INIT_STATIC_SPEC ("md_exec_prefix",		&md_exec_prefix),
-- 
2.23.0