rust: Do not link with libdl and libpthread unconditionally

ChangeLog:

	* Makefile.tpl: Add CRAB1_LIBS variable.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Check if -ldl and -lpthread are needed, and if so, add
	them to CRAB1_LIBS.

gcc/rust/ChangeLog:

	* Make-lang.in: Remove overazealous LIBS = -ldl -lpthread line, link
	crab1 against CRAB1_LIBS.

Makefile.in

@@ -197,6 +197,7 @@ HOST_EXPORTS = \
 	$(BASE_EXPORTS) \
 	CC="$(CC)"; export CC; \
 	ADA_CFLAGS="$(ADA_CFLAGS)"; export ADA_CFLAGS; \
+	CRAB1_LIBS="$(CRAB1_LIBS)"; export CRAB1_LIBS; \
 	CFLAGS="$(CFLAGS)"; export CFLAGS; \
 	CONFIG_SHELL="$(SHELL)"; export CONFIG_SHELL; \
 	CXX="$(CXX)"; export CXX; \
@@ -450,6 +451,8 @@ GOCFLAGS = $(CFLAGS)
 GDCFLAGS = @GDCFLAGS@
 GM2FLAGS = $(CFLAGS)
 
+CRAB1_LIBS = @CRAB1_LIBS@
+
 PKG_CONFIG_PATH = @PKG_CONFIG_PATH@
 
 GUILE = guile

Makefile.tpl

@@ -200,6 +200,7 @@ HOST_EXPORTS = \
 	$(BASE_EXPORTS) \
 	CC="$(CC)"; export CC; \
 	ADA_CFLAGS="$(ADA_CFLAGS)"; export ADA_CFLAGS; \
+	CRAB1_LIBS="$(CRAB1_LIBS)"; export CRAB1_LIBS; \
 	CFLAGS="$(CFLAGS)"; export CFLAGS; \
 	CONFIG_SHELL="$(SHELL)"; export CONFIG_SHELL; \
 	CXX="$(CXX)"; export CXX; \
@@ -453,6 +454,8 @@ GOCFLAGS = $(CFLAGS)
 GDCFLAGS = @GDCFLAGS@
 GM2FLAGS = $(CFLAGS)
 
+CRAB1_LIBS = @CRAB1_LIBS@
+
 PKG_CONFIG_PATH = @PKG_CONFIG_PATH@
 
 GUILE = guile

configure

@@ -690,6 +690,7 @@ extra_host_zlib_configure_flags
 extra_host_libiberty_configure_flags
 stage1_languages
 host_libs_picflag
+CRAB1_LIBS
 PICFLAG
 host_shared
 gcc_host_pie
@@ -8826,6 +8827,139 @@ fi
 
 
 
+# Rust requires -ldl and -lpthread if you are using an old glibc that does not include them by
+# default, so we check for them here
+
+missing_rust_dynlibs=none
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing dlopen" >&5
+$as_echo_n "checking for library containing dlopen... " >&6; }
+if ${ac_cv_search_dlopen+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char dlopen ();
+int
+main ()
+{
+return dlopen ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' dl; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_dlopen=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if ${ac_cv_search_dlopen+:} false; then :
+  break
+fi
+done
+if ${ac_cv_search_dlopen+:} false; then :
+
+else
+  ac_cv_search_dlopen=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_dlopen" >&5
+$as_echo "$ac_cv_search_dlopen" >&6; }
+ac_res=$ac_cv_search_dlopen
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing pthread_create" >&5
+$as_echo_n "checking for library containing pthread_create... " >&6; }
+if ${ac_cv_search_pthread_create+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char pthread_create ();
+int
+main ()
+{
+return pthread_create ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' pthread; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_pthread_create=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if ${ac_cv_search_pthread_create+:} false; then :
+  break
+fi
+done
+if ${ac_cv_search_pthread_create+:} false; then :
+
+else
+  ac_cv_search_pthread_create=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_pthread_create" >&5
+$as_echo "$ac_cv_search_pthread_create" >&6; }
+ac_res=$ac_cv_search_pthread_create
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+fi
+
+
+if test $ac_cv_search_dlopen = -ldl; then
+    CRAB1_LIBS="$CRAB1_LIBS -ldl"
+elif test $ac_cv_search_dlopen = no; then
+    missing_rust_dynlibs="libdl"
+fi
+
+if test $ac_cv_search_pthread_create = -lpthread; then
+    CRAB1_LIBS="$CRAB1_LIBS -lpthread"
+elif test $ac_cv_search_pthread_crate = no; then
+    missing_rust_dynlibs="$missing_rust_dynlibs, libpthread"
+fi
+
+CRAB1_LIBS="$CRAB1_LIBS"
+
+
 # If we are building PIC/PIE host executables, and we are building dependent
 # libs (e.g. GMP) in-tree those libs need to be configured to generate PIC
 # code.
@@ -9066,6 +9200,26 @@ $as_echo "$as_me: WARNING: GDC is required to build $language" >&2;}
             ;;
         esac
 
+        # Disable Rust if we are missing some required C libraries for the Rust runtime.
+        case ${add_this_lang}:${language}:${missing_rust_dynlibs} in
+          *:rust:none)
+            # Nothing to do - we're not missing any C libraries
+            ;;
+          yes:rust:*)
+            as_fn_error $? "some C libraries are required to build $language: $missing_rust_dynlibs" "$LINENO" 5
+            add_this_lang=unsupported
+            ;;
+          all:rust:*)
+            { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: some C libraries are required to build $language: $missing_rust_dynlibs" >&5
+$as_echo "$as_me: WARNING: some C libraries are required to build $language: $missing_rust_dynlibs" >&2;}
+            add_this_lang=unsupported
+            ;;
+          *:rust:*)
+            # Silently disable.
+            add_this_lang=unsupported
+            ;;
+        esac
+
         # Disable jit if -enable-host-shared not specified
         # but not if building for Mingw. All code in Windows
         # is position independent code (PIC).

configure.ac

@@ -2036,6 +2036,28 @@ fi
 
 AC_SUBST(PICFLAG)
 
+# Rust requires -ldl and -lpthread if you are using an old glibc that does not include them by
+# default, so we check for them here
+
+missing_rust_dynlibs=none
+
+AC_SEARCH_LIBS([dlopen], [dl])
+AC_SEARCH_LIBS([pthread_create], [pthread])
+
+if test $ac_cv_search_dlopen = -ldl; then
+    CRAB1_LIBS="$CRAB1_LIBS -ldl"
+elif test $ac_cv_search_dlopen = no; then
+    missing_rust_dynlibs="libdl"
+fi
+
+if test $ac_cv_search_pthread_create = -lpthread; then
+    CRAB1_LIBS="$CRAB1_LIBS -lpthread"
+elif test $ac_cv_search_pthread_crate = no; then
+    missing_rust_dynlibs="$missing_rust_dynlibs, libpthread"
+fi
+
+AC_SUBST(CRAB1_LIBS, "$CRAB1_LIBS")
+
 # If we are building PIC/PIE host executables, and we are building dependent
 # libs (e.g. GMP) in-tree those libs need to be configured to generate PIC
 # code.
@@ -2273,6 +2295,25 @@ if test -d ${srcdir}/gcc; then
             ;;
         esac
 
+        # Disable Rust if we are missing some required C libraries for the Rust runtime.
+        case ${add_this_lang}:${language}:${missing_rust_dynlibs} in
+          *:rust:none)
+            # Nothing to do - we're not missing any C libraries
+            ;;
+          yes:rust:*)
+            AC_MSG_ERROR([some C libraries are required to build $language: $missing_rust_dynlibs])
+            add_this_lang=unsupported
+            ;;
+          all:rust:*)
+            AC_MSG_WARN([some C libraries are required to build $language: $missing_rust_dynlibs])
+            add_this_lang=unsupported
+            ;;
+          *:rust:*)
+            # Silently disable.
+            add_this_lang=unsupported
+            ;;
+        esac
+
         # Disable jit if -enable-host-shared not specified
         # but not if building for Mingw. All code in Windows
         # is position independent code (PIC).

gcc/rust/Make-lang.in

@@ -54,8 +54,6 @@ GCCRS_D_OBJS = \
    rust/rustspec.o \
    $(END)
 
-LIBS += -ldl -lpthread
-
 gccrs$(exeext): $(GCCRS_D_OBJS) $(EXTRA_GCC_OBJS) libcommon-target.a $(LIBDEPS)
 	+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
 	  $(GCCRS_D_OBJS) $(EXTRA_GCC_OBJS) libcommon-target.a \
@@ -234,7 +232,7 @@ crab1$(exeext): $(RUST_ALL_OBJS) attribs.o $(BACKEND) $(LIBDEPS) $(LIBPROC_MACRO
 	@$(call LINK_PROGRESS,$(INDEX.rust),start)
 	+$(LLINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
 	      $(RUST_ALL_OBJS) attribs.o $(BACKEND) \
-	      $(LIBS) $(LIBPROC_MACRO_INTERNAL) $(LIBFORMAT_PARSER) $(LIBFFI_POLONIUS) \
+	      $(LIBS) $(CRAB1_LIBS) $(LIBPROC_MACRO_INTERNAL) $(LIBFORMAT_PARSER) $(LIBFFI_POLONIUS) \
  		  $(BACKENDLIBS)
 	@$(call LINK_PROGRESS,$(INDEX.rust),end)
 
@@ -496,4 +494,4 @@ rust/libffi_polonius.a: \
 	rust/checks/errors/borrowck/ffi-polonius/Cargo.toml \
 	$(wildcard $(srcdir)/rust/checks/errors/borrowck/ffi-polonius/src/*)
 	cargo build --manifest-path $(srcdir)/rust/checks/errors/borrowck/ffi-polonius/Cargo.toml --release --target-dir rust/ffi-polonius
-	cp rust/ffi-polonius/release/libffi_polonius.a rust/libffi_polonius.a
+	cp rust/ffi-polonius/release/libffi_polonius.a rust/libffi_polonius.a