Re: [PATCH, v3] Potential solution to librt issue.

[Paolo Bonzini <bonzini at gnu dot org>]

> Paolo, can you help us (Chris) with the "automagic" thing?

I did something in the attached patch (not even compiled) but I'm not 
sure it's the right approach at all.  The idea is to allow inserting 
language-specific stuff in the config/*.h files.

Note that it's the first time I touch specs, and I'm not sure if this 
actually could work for the -static case.

Paolo
Index: gcc.c
===================================================================
--- gcc.c	(revision 134435)
+++ gcc.c	(working copy)
@@ -361,6 +361,7 @@ static const char *convert_filename (con
 static const char *getenv_spec_function (int, const char **);
 static const char *if_exists_spec_function (int, const char **);
 static const char *if_exists_else_spec_function (int, const char **);
+static const char *if_language_spec_function (int, const char **);
 static const char *replace_outfile_spec_function (int, const char **);
 static const char *version_compare_spec_function (int, const char **);
 static const char *include_spec_function (int, const char **);
@@ -1634,6 +1635,7 @@ static const struct spec_function static
   { "getenv",                   getenv_spec_function },
   { "if-exists",		if_exists_spec_function },
   { "if-exists-else",		if_exists_else_spec_function },
+  { "if-language",		if_language_spec_function },
   { "replace-outfile",		replace_outfile_spec_function },
   { "version-compare",		version_compare_spec_function },
   { "include",			include_spec_function },
@@ -7800,6 +7802,24 @@ if_exists_else_spec_function (int argc, 
   return argv[1];
 }
 
+/* if-language built-in spec function.
+
+   Expands to the second argument if the current driver is the
+   string in the first argument.  */
+
+static const char *
+if_language_spec_function (int argc, const char **argv)
+{
+  /* Must have exactly two arguments.  */
+  if (argc != 2)
+    return NULL;
+
+  if (!strcmp (lang_driver_name, argv[0]))
+    return argv[1];
+
+  return NULL;
+}
+
 /* replace-outfile built-in spec function.
 
    This looks for the first argument in the outfiles array's name and
Index: gcc.h
===================================================================
--- gcc.h	(revision 134435)
+++ gcc.h	(working copy)
@@ -74,6 +74,9 @@ extern int n_infiles;
 /* Number of extra output files that lang_specific_pre_link may generate.  */
 extern int lang_specific_extra_outfiles;
 
+/* Driver name for the if-language function.  */
+extern const char *lang_driver_name;
+
 /* A vector of corresponding output files is made up later.  */
 
 extern const char **outfiles;
Index: cppspec.c
===================================================================
--- cppspec.c	(revision 134435)
+++ cppspec.c	(working copy)
@@ -208,3 +208,6 @@ int lang_specific_pre_link (void)
 
 /* Number of extra output files that lang_specific_pre_link may generate.  */
 int lang_specific_extra_outfiles = 0;  /* Not used for cpp.  */
+
+/* Driver name.  */
+const char *lang_driver_name = "cpp";
Index: gccspec.c
===================================================================
--- gccspec.c	(revision 134435)
+++ gccspec.c	(working copy)
@@ -104,3 +104,6 @@ lang_specific_pre_link (void)
 
 /* Number of extra output files that lang_specific_pre_link may generate.  */
 int lang_specific_extra_outfiles = 0;  /* Not used for C.  */
+
+/* Driver name.  */
+const char *lang_driver_name = "gcc";
Index: cp/g++spec.c
===================================================================
--- cp/g++spec.c	(revision 134435)
+++ cp/g++spec.c	(working copy)
@@ -349,3 +349,6 @@ int lang_specific_pre_link (void)  /* No
 
 /* Number of extra output files that lang_specific_pre_link may generate.  */
 int lang_specific_extra_outfiles = 0;  /* Not used for C++.  */
+
+/* Driver name.  */
+const char *lang_driver_name = "g++";
Index: fortran/gfortranspec.c
===================================================================
--- fortran/gfortranspec.c	(revision 134435)
+++ fortran/gfortranspec.c	(working copy)
@@ -584,3 +584,6 @@ lang_specific_pre_link (void)	/* Not use
 
 /* Number of extra output files that lang_specific_pre_link may generate.  */
 int lang_specific_extra_outfiles = 0;	/* Not used for F77.  */
+
+/* Driver name.  */
+const char *lang_driver_name = "gfortran";
Index: java/jvspec.c
===================================================================
--- java/jvspec.c	(revision 134435)
+++ java/jvspec.c	(working copy)
@@ -685,3 +685,6 @@ lang_specific_pre_link (void)
     }
   return err;
 }
+
+/* Driver name.  */
+const char *lang_driver_name = "gcj";
Index: config/linux.h
===================================================================
--- config/linux.h	(revision 134435)
+++ config/linux.h	(working copy)
@@ -67,12 +67,25 @@ along with GCC; see the file COPYING3.  
 #undef CPLUSPLUS_CPP_SPEC
 #define CPLUSPLUS_CPP_SPEC "-D_GNU_SOURCE %(cpp)"
 
-#undef	LIB_SPEC
-#define LIB_SPEC \
+#undef	BASE_LIB_SPEC
+#define BASE_LIB_SPEC \
   "%{pthread:-lpthread} \
    %{shared:-lc} \
    %{!shared:%{mieee-fp:-lieee} %{profile:-lc_p}%{!profile:-lc}}"
 
+#ifndef HAVE_LD_AS_NEEDED
+#define BASE_LIB_SPEC LIB_SPEC
+#define BASE_LIB_SPEC LIB_SPEC " \
+   %{!nostdlib:%{!nodefaultlibs:%:if-language(g++, -lrt )}}"
+
+#else
+#define BASE_LIB_SPEC LIB_SPEC " \
+   %{!nostdlib:%{!nodefaultlibs:%:if-language(g++, --as-needed -lrt --no-as-needed )}}"
+
+/* Use --as-needed -lgcc_s for eh support.  */
+#define USE_LD_AS_NEEDED 1
+#else
+
 #define LINUX_TARGET_OS_CPP_BUILTINS()				\
     do {							\
 	builtin_define ("__gnu_linux__");			\
@@ -94,11 +107,6 @@ along with GCC; see the file COPYING3.  
 #define LINK_GCC_C_SEQUENCE_SPEC \
   "%{static:--start-group} %G %L %{static:--end-group}%{!static:%G}"
 
-/* Use --as-needed -lgcc_s for eh support.  */
-#ifdef HAVE_LD_AS_NEEDED
-#define USE_LD_AS_NEEDED 1
-#endif
-
 /* Determine which dynamic linker to use depending on whether GLIBC or
    uClibc is the default C library and whether -muclibc or -mglibc has
    been passed to change the default.  */