rust: Do not link with libdl and libpthread unconditionally

Message ID 20240419094903.512887-1-arthur.cohen@embecosm.com
State New
Headers
Series rust: Do not link with libdl and libpthread unconditionally |

Checks

Context Check Description
linaro-tcwg-bot/tcwg_gcc_build--master-aarch64 success Testing passed
linaro-tcwg-bot/tcwg_gcc_check--master-aarch64 success Testing passed
linaro-tcwg-bot/tcwg_gcc_build--master-arm success Testing passed
linaro-tcwg-bot/tcwg_gcc_check--master-arm success Testing passed

Commit Message

Arthur Cohen April 19, 2024, 9:47 a.m. UTC
  Hi everyone,

This patch checks for the presence of dlopen and pthread_create in libc. If that is not the
case, we check for the existence of -ldl and -lpthread, as these libraries are required to
link the Rust runtime to our Rust frontend.

If these libs are not present on the system, then we disable the Rust frontend.

This was tested on x86_64, in an environment with a recent GLIBC and in a container with GLIBC
2.27.

Apologies for sending it in so late.

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           |   3 +
 Makefile.tpl          |   3 +
 configure             | 157 ++++++++++++++++++++++++++++++++++++++++++
 configure.ac          |  94 +++++++++++++++++++++++++
 gcc/rust/Make-lang.in |   2 +-
 5 files changed, 258 insertions(+), 1 deletion(-)
  

Comments

Richard Biener April 30, 2024, 7:55 a.m. UTC | #1
On Fri, Apr 19, 2024 at 11:49 AM Arthur Cohen <arthur.cohen@embecosm.com> wrote:
>
> Hi everyone,
>
> This patch checks for the presence of dlopen and pthread_create in libc. If that is not the
> case, we check for the existence of -ldl and -lpthread, as these libraries are required to
> link the Rust runtime to our Rust frontend.
>
> If these libs are not present on the system, then we disable the Rust frontend.
>
> This was tested on x86_64, in an environment with a recent GLIBC and in a container with GLIBC
> 2.27.
>
> Apologies for sending it in so late.

For example GCC_ENABLE_PLUGINS simply does

     # Check -ldl
     saved_LIBS="$LIBS"
     AC_SEARCH_LIBS([dlopen], [dl])
     if test x"$ac_cv_search_dlopen" = x"-ldl"; then
       pluginlibs="$pluginlibs -ldl"
     fi
     LIBS="$saved_LIBS"

which I guess would also work for pthread_create?  This would simplify
the code a bit.

> 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           |   3 +
>  Makefile.tpl          |   3 +
>  configure             | 157 ++++++++++++++++++++++++++++++++++++++++++
>  configure.ac          |  94 +++++++++++++++++++++++++
>  gcc/rust/Make-lang.in |   2 +-
>  5 files changed, 258 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile.in b/Makefile.in
> index db4fa6c6260..34c5550beca 100644
> --- a/Makefile.in
> +++ b/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
> diff --git a/Makefile.tpl b/Makefile.tpl
> index 1d5813cd569..8f4bf297918 100644
> --- a/Makefile.tpl
> +++ b/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
> diff --git a/configure b/configure
> index 3b0abeb8b2e..75b489a5f57 100755
> --- a/configure
> +++ b/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
> @@ -8875,6 +8876,142 @@ 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
> +
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if libc includes libdl and libpthread" >&5
> +$as_echo_n "checking if libc includes libdl and libpthread... " >&6; }
> +
> +ac_ext=c
> +ac_cpp='$CPP $CPPFLAGS'
> +ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> +ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
> +ac_compiler_gnu=$ac_cv_c_compiler_gnu
> +
> +
> +requires_ldl=no
> +requires_lpthread=no
> +missing_rust_dynlibs=none
> +
> +cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +/* end confdefs.h.  */
> +#include <dlfcn.h>
> +int
> +main ()
> +{
> +dlopen(0,0);
> +  ;
> +  return 0;
> +}
> +_ACEOF
> +if ac_fn_c_try_link "$LINENO"; then :
> +
> +else
> +  requires_ldl=yes
> +
> +fi
> +rm -f core conftest.err conftest.$ac_objext \
> +    conftest$ac_exeext conftest.$ac_ext
> +
> +if test $requires_ldl = yes; then
> +    tmp_LIBS=$LIBS
> +    LIBS="$LIBS -ldl"
> +
> +    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +/* end confdefs.h.  */
> +#include <dlfcn.h>
> +int
> +main ()
> +{
> +dlopen(0,0);
> +  ;
> +  return 0;
> +}
> +_ACEOF
> +if ac_fn_c_try_link "$LINENO"; then :
> +  CRAB1_LIBS="$CRAB1_LIBS -ldl"
> +else
> +  missing_rust_dynlibs="libdl"
> +
> +fi
> +rm -f core conftest.err conftest.$ac_objext \
> +    conftest$ac_exeext conftest.$ac_ext
> +
> +    LIBS=$tmp_LIBS
> +fi
> +
> +cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +/* end confdefs.h.  */
> +#include <pthread.h>
> +int
> +main ()
> +{
> +pthread_create(NULL,NULL,NULL,NULL);
> +
> +  ;
> +  return 0;
> +}
> +_ACEOF
> +if ac_fn_c_try_link "$LINENO"; then :
> +
> +else
> +  requires_lpthread=yes
> +
> +fi
> +rm -f core conftest.err conftest.$ac_objext \
> +    conftest$ac_exeext conftest.$ac_ext
> +
> +if test $requires_lpthread = yes; then
> +    tmp_LIBS=$LIBS
> +    LIBS="$LIBS -lpthread"
> +
> +    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +/* end confdefs.h.  */
> +#include <pthread.h>
> +int
> +main ()
> +{
> +pthread_create(NULL,NULL,NULL,NULL);
> +
> +  ;
> +  return 0;
> +}
> +_ACEOF
> +if ac_fn_c_try_link "$LINENO"; then :
> +  CRAB1_LIBS="$CRAB1_LIBS -lpthread"
> +else
> +  missing_rust_dynlibs="$missing_rust_dynlibs, libpthread"
> +
> +fi
> +rm -f core conftest.err conftest.$ac_objext \
> +    conftest$ac_exeext conftest.$ac_ext
> +
> +    LIBS=$tmp_LIBS
> +fi
> +
> +if test "$missing_rust_dynlibs" = "none"; then
> +  if test $requires_ldl = yes -a $requires_lpthread = yes; then
> +    { $as_echo "$as_me:${as_lineno-$LINENO}: result: not included, but available" >&5
> +$as_echo "not included, but available" >&6; }
> +  else
> +    { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
> +$as_echo "yes" >&6; }
> +  fi
> +else
> +  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no: missing $missing_rust_dynlibs" >&5
> +$as_echo "no: missing $missing_rust_dynlibs" >&6; }
> +fi
> +
> +CRAB1_LIBS="$CRAB1_LIBS"
> +
> +
> +ac_ext=c
> +ac_cpp='$CPP $CPPFLAGS'
> +ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> +ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
> +ac_compiler_gnu=$ac_cv_c_compiler_gnu
> +
> +
>  # 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.
> @@ -9115,6 +9252,26 @@ $as_echo "$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).
> diff --git a/configure.ac b/configure.ac
> index 042681c27be..d96b7b5432e 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -2037,6 +2037,81 @@ 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
> +
> +AC_MSG_CHECKING([if libc includes libdl and libpthread])
> +
> +AC_LANG_PUSH([C])
> +
> +requires_ldl=no
> +requires_lpthread=no
> +missing_rust_dynlibs=none
> +
> +AC_LINK_IFELSE(
> +  [AC_LANG_PROGRAM(
> +    [#include <dlfcn.h>],
> +    [dlopen(0,0);],
> +  )],
> +  [],
> +  [requires_ldl=yes]
> +)
> +
> +if test $requires_ldl = yes; then
> +    tmp_LIBS=$LIBS
> +    LIBS="$LIBS -ldl"
> +
> +    AC_LINK_IFELSE(
> +      [AC_LANG_PROGRAM(
> +        [#include <dlfcn.h>],
> +        [dlopen(0,0);],
> +      )],
> +      [CRAB1_LIBS="$CRAB1_LIBS -ldl"],
> +      [missing_rust_dynlibs="libdl"]
> +    )
> +
> +    LIBS=$tmp_LIBS
> +fi
> +
> +AC_LINK_IFELSE(
> +  [AC_LANG_PROGRAM(
> +    [#include <pthread.h>],
> +    [pthread_create(NULL,NULL,NULL,NULL);]
> +  )],
> +  [],
> +  [requires_lpthread=yes]
> +)
> +
> +if test $requires_lpthread = yes; then
> +    tmp_LIBS=$LIBS
> +    LIBS="$LIBS -lpthread"
> +
> +    AC_LINK_IFELSE(
> +      [AC_LANG_PROGRAM(
> +        [#include <pthread.h>],
> +        [pthread_create(NULL,NULL,NULL,NULL);]
> +      )],
> +      [CRAB1_LIBS="$CRAB1_LIBS -lpthread"],
> +      [missing_rust_dynlibs="$missing_rust_dynlibs, libpthread"]
> +    )
> +
> +    LIBS=$tmp_LIBS
> +fi
> +
> +if test "$missing_rust_dynlibs" = "none"; then
> +  if test $requires_ldl = yes -a $requires_lpthread = yes; then
> +    AC_MSG_RESULT([not included, but available])
> +  else
> +    AC_MSG_RESULT([yes])
> +  fi
> +else
> +  AC_MSG_RESULT([no: missing $missing_rust_dynlibs])
> +fi
> +
> +AC_SUBST(CRAB1_LIBS, "$CRAB1_LIBS")
> +
> +AC_LANG_POP([C])
> +
>  # 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.
> @@ -2274,6 +2349,25 @@ 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: $missing_rust_dynlibs])
> +            add_this_lang=unsupported
> +            ;;
> +          *:rust:*)
> +            # Silently disable.
> +            add_this_lang=unsupported
> +            ;;
> +        esac
> +
>          # Disable jit if -enable-host-shared not specified
>          # but not if building for Mingw. All code in Windows
>          # is position independent code (PIC).
> diff --git a/gcc/rust/Make-lang.in b/gcc/rust/Make-lang.in
> index 8db04163618..bb2e246f9fa 100644
> --- a/gcc/rust/Make-lang.in
> +++ b/gcc/rust/Make-lang.in
> @@ -214,7 +214,7 @@ LIBPROC_MACRO_INTERNAL = ../libgrust/libproc_macro_internal/libproc_macro_intern
>  crab1$(exeext): $(RUST_ALL_OBJS) attribs.o $(BACKEND) $(LIBDEPS) $(LIBPROC_MACRO_INTERNAL) $(rust.prev)
>         @$(call LINK_PROGRESS,$(INDEX.rust),start)
>         +$(LLINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
> -             $(RUST_ALL_OBJS) attribs.o $(BACKEND) $(LIBS) $(LIBPROC_MACRO_INTERNAL) $(BACKENDLIBS)
> +             $(RUST_ALL_OBJS) attribs.o $(BACKEND) $(LIBS) $(CRAB1_LIBS) $(LIBPROC_MACRO_INTERNAL) $(BACKENDLIBS)
>         @$(call LINK_PROGRESS,$(INDEX.rust),end)
>
>  # Build hooks.
> --
> 2.42.1
>
  

Patch

diff --git a/Makefile.in b/Makefile.in
index db4fa6c6260..34c5550beca 100644
--- a/Makefile.in
+++ b/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
diff --git a/Makefile.tpl b/Makefile.tpl
index 1d5813cd569..8f4bf297918 100644
--- a/Makefile.tpl
+++ b/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
diff --git a/configure b/configure
index 3b0abeb8b2e..75b489a5f57 100755
--- a/configure
+++ b/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
@@ -8875,6 +8876,142 @@  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
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if libc includes libdl and libpthread" >&5
+$as_echo_n "checking if libc includes libdl and libpthread... " >&6; }
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
+requires_ldl=no
+requires_lpthread=no
+missing_rust_dynlibs=none
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <dlfcn.h>
+int
+main ()
+{
+dlopen(0,0);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+
+else
+  requires_ldl=yes
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+if test $requires_ldl = yes; then
+    tmp_LIBS=$LIBS
+    LIBS="$LIBS -ldl"
+
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <dlfcn.h>
+int
+main ()
+{
+dlopen(0,0);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  CRAB1_LIBS="$CRAB1_LIBS -ldl"
+else
+  missing_rust_dynlibs="libdl"
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+    LIBS=$tmp_LIBS
+fi
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+pthread_create(NULL,NULL,NULL,NULL);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+
+else
+  requires_lpthread=yes
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+if test $requires_lpthread = yes; then
+    tmp_LIBS=$LIBS
+    LIBS="$LIBS -lpthread"
+
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+pthread_create(NULL,NULL,NULL,NULL);
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  CRAB1_LIBS="$CRAB1_LIBS -lpthread"
+else
+  missing_rust_dynlibs="$missing_rust_dynlibs, libpthread"
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+    LIBS=$tmp_LIBS
+fi
+
+if test "$missing_rust_dynlibs" = "none"; then
+  if test $requires_ldl = yes -a $requires_lpthread = yes; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: not included, but available" >&5
+$as_echo "not included, but available" >&6; }
+  else
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+  fi
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no: missing $missing_rust_dynlibs" >&5
+$as_echo "no: missing $missing_rust_dynlibs" >&6; }
+fi
+
+CRAB1_LIBS="$CRAB1_LIBS"
+
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
 # 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.
@@ -9115,6 +9252,26 @@  $as_echo "$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).
diff --git a/configure.ac b/configure.ac
index 042681c27be..d96b7b5432e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2037,6 +2037,81 @@  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
+
+AC_MSG_CHECKING([if libc includes libdl and libpthread])
+
+AC_LANG_PUSH([C])
+
+requires_ldl=no
+requires_lpthread=no
+missing_rust_dynlibs=none
+
+AC_LINK_IFELSE(
+  [AC_LANG_PROGRAM(
+    [#include <dlfcn.h>],
+    [dlopen(0,0);],
+  )],
+  [],
+  [requires_ldl=yes]
+)
+
+if test $requires_ldl = yes; then
+    tmp_LIBS=$LIBS
+    LIBS="$LIBS -ldl"
+
+    AC_LINK_IFELSE(
+      [AC_LANG_PROGRAM(
+        [#include <dlfcn.h>],
+        [dlopen(0,0);],
+      )],
+      [CRAB1_LIBS="$CRAB1_LIBS -ldl"],
+      [missing_rust_dynlibs="libdl"]
+    )
+
+    LIBS=$tmp_LIBS
+fi
+
+AC_LINK_IFELSE(
+  [AC_LANG_PROGRAM(
+    [#include <pthread.h>],
+    [pthread_create(NULL,NULL,NULL,NULL);]
+  )],
+  [],
+  [requires_lpthread=yes]
+)
+
+if test $requires_lpthread = yes; then
+    tmp_LIBS=$LIBS
+    LIBS="$LIBS -lpthread"
+
+    AC_LINK_IFELSE(
+      [AC_LANG_PROGRAM(
+        [#include <pthread.h>],
+        [pthread_create(NULL,NULL,NULL,NULL);]
+      )],
+      [CRAB1_LIBS="$CRAB1_LIBS -lpthread"],
+      [missing_rust_dynlibs="$missing_rust_dynlibs, libpthread"]
+    )
+
+    LIBS=$tmp_LIBS
+fi
+
+if test "$missing_rust_dynlibs" = "none"; then
+  if test $requires_ldl = yes -a $requires_lpthread = yes; then
+    AC_MSG_RESULT([not included, but available])
+  else
+    AC_MSG_RESULT([yes])
+  fi
+else
+  AC_MSG_RESULT([no: missing $missing_rust_dynlibs])
+fi
+
+AC_SUBST(CRAB1_LIBS, "$CRAB1_LIBS")
+
+AC_LANG_POP([C])
+
 # 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.
@@ -2274,6 +2349,25 @@  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: $missing_rust_dynlibs])
+            add_this_lang=unsupported
+            ;;
+          *:rust:*)
+            # Silently disable.
+            add_this_lang=unsupported
+            ;;
+        esac
+
         # Disable jit if -enable-host-shared not specified
         # but not if building for Mingw. All code in Windows
         # is position independent code (PIC).
diff --git a/gcc/rust/Make-lang.in b/gcc/rust/Make-lang.in
index 8db04163618..bb2e246f9fa 100644
--- a/gcc/rust/Make-lang.in
+++ b/gcc/rust/Make-lang.in
@@ -214,7 +214,7 @@  LIBPROC_MACRO_INTERNAL = ../libgrust/libproc_macro_internal/libproc_macro_intern
 crab1$(exeext): $(RUST_ALL_OBJS) attribs.o $(BACKEND) $(LIBDEPS) $(LIBPROC_MACRO_INTERNAL) $(rust.prev)
 	@$(call LINK_PROGRESS,$(INDEX.rust),start)
 	+$(LLINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
-	      $(RUST_ALL_OBJS) attribs.o $(BACKEND) $(LIBS) $(LIBPROC_MACRO_INTERNAL) $(BACKENDLIBS)
+	      $(RUST_ALL_OBJS) attribs.o $(BACKEND) $(LIBS) $(CRAB1_LIBS) $(LIBPROC_MACRO_INTERNAL) $(BACKENDLIBS)
 	@$(call LINK_PROGRESS,$(INDEX.rust),end)
 
 # Build hooks.