Add '-Wno-complain-wrong-lang', and use it in 'gcc/testsuite/lib/target-supports.exp:check_compile' and elsewhere

I noticed that GCC/Rust recently lost all LTO variants in torture testing:

     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O0  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O1  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2  (test for excess errors)
    -PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fno-use-linker-plugin -flto-partition=none  (test for excess errors)
    -PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O3 -g  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -Os  (test for excess errors)

Etc.

The reason is that when probing for availability of LTO, we run into:

    spawn [...]/build-gcc/gcc/testsuite/rust/../../gccrs -B[...]/build-gcc/gcc/testsuite/rust/../../ -fdiagnostics-plain-output -frust-incomplete-and-experimental-compiler-do-not-use -flto -c -o lto8274.o lto8274.c
    cc1: warning: command-line option '-frust-incomplete-and-experimental-compiler-do-not-use' is valid for Rust but not for C

For GCC/Rust testing, this flag is (as of recently) defaulted in
'gcc/testsuite/lib/rust.exp:rust_init':

    lappend ALWAYS_RUSTFLAGS "additional_flags=-frust-incomplete-and-experimental-compiler-do-not-use"

A few more "command-line option [...] is valid for [...] but not for [...]"
instances were found in the test suite logs, when more than one language is
involved.

With '-Wno-complain-wrong-lang' used in
'gcc/testsuite/lib/target-supports.exp:check_compile', we get back:

     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O0  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O1  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2  (test for excess errors)
    +PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fno-use-linker-plugin -flto-partition=none  (test for excess errors)
    +PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -O3 -g  (test for excess errors)
     PASS: rust/compile/torture/all_doc_comment_line_blocks.rs   -Os  (test for excess errors)

Etc., and in total:

                    === rust Summary for unix ===

    # of expected passes            [-4990-]{+6718+}
    # of expected failures          [-39-]{+51+}

Anything that 'gcc/opts-global.cc:complain_wrong_lang' might do is cut
short by '-Wno-complain-wrong-lang', not just the one 'warning'
diagnostic.  This corresponds to what already exists via
'lang_hooks.complain_wrong_lang_p'.

The 'gcc/opts-common.cc:prune_options' changes follow the same rationale
as PR67640 "driver passes -fdiagnostics-color= always last": we need to
process '-Wno-complain-wrong-lang' early, so that it properly affects
other options appearing before it on the command line.

	gcc/
	* common.opt (-Wcomplain-wrong-lang): New.
	* doc/invoke.texi (-Wno-complain-wrong-lang): Document it.
	* opts-common.cc (prune_options): Handle it.
	* opts-global.cc (complain_wrong_lang): Use it.
	gcc/testsuite/
	* gcc.dg/Wcomplain-wrong-lang-1.c: New.
	* gcc.dg/Wcomplain-wrong-lang-2.c: Likewise.
	* gcc.dg/Wcomplain-wrong-lang-3.c: Likewise.
	* gcc.dg/Wcomplain-wrong-lang-4.c: Likewise.
	* gcc.dg/Wcomplain-wrong-lang-5.c: Likewise.
	* lib/target-supports.exp (check_compile): Use
	'-Wno-complain-wrong-lang'.
	* g++.dg/abi/empty12.C: Likewise.
	* g++.dg/abi/empty13.C: Likewise.
	* g++.dg/abi/empty14.C: Likewise.
	* g++.dg/abi/empty15.C: Likewise.
	* g++.dg/abi/empty16.C: Likewise.
	* g++.dg/abi/empty17.C: Likewise.
	* g++.dg/abi/empty18.C: Likewise.
	* g++.dg/abi/empty19.C: Likewise.
	* g++.dg/abi/empty22.C: Likewise.
	* g++.dg/abi/empty25.C: Likewise.
	* g++.dg/abi/empty26.C: Likewise.
	* gfortran.dg/bind-c-contiguous-1.f90: Likewise.
	* gfortran.dg/bind-c-contiguous-4.f90: Likewise.
	* gfortran.dg/bind-c-contiguous-5.f90: Likewise.
	libgomp/
	* testsuite/libgomp.fortran/alloc-10.f90: Use
	'-Wno-complain-wrong-lang'.
	* testsuite/libgomp.fortran/alloc-11.f90: Likewise.
	* testsuite/libgomp.fortran/alloc-7.f90: Likewise.
	* testsuite/libgomp.fortran/alloc-9.f90: Likewise.
	* testsuite/libgomp.fortran/allocate-1.f90: Likewise.
	* testsuite/libgomp.fortran/depend-4.f90: Likewise.
	* testsuite/libgomp.fortran/depend-5.f90: Likewise.
	* testsuite/libgomp.fortran/depend-6.f90: Likewise.
	* testsuite/libgomp.fortran/depend-7.f90: Likewise.
	* testsuite/libgomp.fortran/depend-inoutset-1.f90: Likewise.
	* testsuite/libgomp.fortran/examples-4/declare_target-1.f90:
	Likewise.
	* testsuite/libgomp.fortran/examples-4/declare_target-2.f90:
	Likewise.
	* testsuite/libgomp.fortran/order-reproducible-1.f90: Likewise.
	* testsuite/libgomp.fortran/order-reproducible-2.f90: Likewise.
	* testsuite/libgomp.oacc-fortran/parallel-dims.f90: Likewise.
	* testsuite/libgomp.fortran/task-detach-6.f90: Remove left-over
	'dg-prune-output'.

24 files changed, 91 insertions, 24 deletions

diff --git a/gcc/common.opt b/gcc/common.opt
index d0371ae..50bcc523 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -582,6 +582,10 @@ Wcast-align=strict
 Common Var(warn_cast_align,2) Warning
 Warn about pointer casts which increase alignment.
 
+Wcomplain-wrong-lang
+Common Var(warn_complain_wrong_lang) Init(1) Warning
+Complain when a command-line option is valid, but not applicable to the current front end.
+
 Wcpp
 Common Var(warn_cpp) Init(1) Warning
 Warn when a #warning directive is encountered.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index bcf8510..a7ec1a9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -343,6 +343,7 @@ Objective-C and Objective-C++ Dialects}.
 -Wcast-align  -Wcast-align=strict  -Wcast-function-type  -Wcast-qual  @gol
 -Wchar-subscripts @gol
 -Wclobbered  -Wcomment @gol
+-Wno-complain-wrong-lang @gol
 -Wconversion  -Wno-coverage-mismatch  -Wno-cpp @gol
 -Wdangling-else  -Wdangling-pointer  -Wdangling-pointer=@var{n}  @gol
 -Wdate-time @gol
@@ -8944,6 +8945,25 @@ programs.
 Warn for variables that might be changed by @code{longjmp} or
 @code{vfork}.  This warning is also enabled by @option{-Wextra}.
 
+@item -Wno-complain-wrong-lang
+@opindex Wcomplain-wrong-lang
+@opindex Wno-complain-wrong-lang
+By default, language front ends complain when a command-line option is
+valid, but not applicable to that front end.
+This may be disabled with @option{-Wno-complain-wrong-lang},
+which is mostly useful when invoking a single compiler driver for
+multiple source files written in different languages, for example:
+
+@smallexample
+$ g++ -fno-rtti a.cc b.f90
+@end smallexample
+
+The driver @file{g++} invokes the C++ front end to compile @file{a.cc}
+and the Fortran front end to compile @file{b.f90}.
+The latter front end diagnoses
+@samp{f951: Warning: command-line option '-fno-rtti' is valid for C++/D/ObjC++ but not for Fortran},
+which may be disabled with @option{-Wno-complain-wrong-lang}.
+
 @item -Wconversion
 @opindex Wconversion
 @opindex Wno-conversion
diff --git a/gcc/opts-common.cc b/gcc/opts-common.cc
index c3ede43..23ddcaa 100644
--- a/gcc/opts-common.cc
+++ b/gcc/opts-common.cc
@@ -1112,7 +1112,8 @@ cancel_option (int opt_idx, int next_opt_idx, int orig_next_opt_idx)
   return false;
 }
 
-/* Filter out options canceled by the ones after them.  */
+/* Filter out options canceled by the ones after them, and related
+   rearrangement.  */
 
 static void
 prune_options (struct cl_decoded_option **decoded_options,
@@ -1125,6 +1126,8 @@ prune_options (struct cl_decoded_option **decoded_options,
     = XNEWVEC (struct cl_decoded_option, old_decoded_options_count);
   unsigned int i;
   const struct cl_option *option;
+  unsigned int options_to_prepend = 0;
+  unsigned int Wcomplain_wrong_lang_idx = 0;
   unsigned int fdiagnostics_color_idx = 0;
 
   /* Remove arguments which are negated by others after them.  */
@@ -1146,8 +1149,17 @@ prune_options (struct cl_decoded_option **decoded_options,
 	case OPT_SPECIAL_input_file:
 	  goto keep;
 
-	/* Do not save OPT_fdiagnostics_color_, just remember the last one.  */
+	/* Do not handle the following yet, just remember the last one.  */
+	case OPT_Wcomplain_wrong_lang:
+	  gcc_checking_assert (i != 0);
+	  if (Wcomplain_wrong_lang_idx == 0)
+	    ++options_to_prepend;
+	  Wcomplain_wrong_lang_idx = i;
+	  continue;
 	case OPT_fdiagnostics_color_:
+	  gcc_checking_assert (i != 0);
+	  if (fdiagnostics_color_idx == 0)
+	    ++options_to_prepend;
 	  fdiagnostics_color_idx = i;
 	  continue;
 
@@ -1191,15 +1203,29 @@ keep:
 	}
     }
 
-  if (fdiagnostics_color_idx >= 1)
+  /* For those not yet handled, put (only) the last at a front position after
+     'argv[0]', so they can take effect immediately.  */
+  if (options_to_prepend)
     {
-      /* We put the last -fdiagnostics-color= at the first position
-	 after argv[0] so it can take effect immediately.  */
-      memmove (new_decoded_options + 2, new_decoded_options + 1,
-	       sizeof (struct cl_decoded_option) 
-	       * (new_decoded_options_count - 1));
-      new_decoded_options[1] = old_decoded_options[fdiagnostics_color_idx];
-      new_decoded_options_count++;
+      const unsigned int argv_0 = 1;
+      memmove (new_decoded_options + argv_0 + options_to_prepend,
+	       new_decoded_options + argv_0,
+	       sizeof (struct cl_decoded_option)
+	       * (new_decoded_options_count - argv_0));
+      unsigned int options_prepended = 0;
+      if (Wcomplain_wrong_lang_idx != 0)
+	{
+	  new_decoded_options[argv_0 + options_prepended++]
+	    = old_decoded_options[Wcomplain_wrong_lang_idx];
+	  new_decoded_options_count++;
+	}
+      if (fdiagnostics_color_idx != 0)
+	{
+	  new_decoded_options[argv_0 + options_prepended++]
+	    = old_decoded_options[fdiagnostics_color_idx];
+	  new_decoded_options_count++;
+	}
+      gcc_checking_assert (options_to_prepend == options_prepended);
     }
 
   free (old_decoded_options);
diff --git a/gcc/opts-global.cc b/gcc/opts-global.cc
index d078384..b7bba23 100644
--- a/gcc/opts-global.cc
+++ b/gcc/opts-global.cc
@@ -91,6 +91,9 @@ complain_wrong_lang (const struct cl_decoded_option *decoded,
   char *ok_langs = NULL, *bad_lang = NULL;
   unsigned int opt_flags = option->flags;
 
+  if (!warn_complain_wrong_lang)
+    return;
+
   if (!lang_hooks.complain_wrong_lang_p (option))
     return;
 
diff --git a/gcc/testsuite/g++.dg/abi/empty12.C b/gcc/testsuite/g++.dg/abi/empty12.C
index 6568fc62..6d67f8d 100644
--- a/gcc/testsuite/g++.dg/abi/empty12.C
+++ b/gcc/testsuite/g++.dg/abi/empty12.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty12a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty12.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty13.C b/gcc/testsuite/g++.dg/abi/empty13.C
index 9ec1887..47f1d73 100644
--- a/gcc/testsuite/g++.dg/abi/empty13.C
+++ b/gcc/testsuite/g++.dg/abi/empty13.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-x c -fabi-version=11" }
 // { dg-additional-sources "empty13a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty13.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty14.C b/gcc/testsuite/g++.dg/abi/empty14.C
index 7deb463..8881beb 100644
--- a/gcc/testsuite/g++.dg/abi/empty14.C
+++ b/gcc/testsuite/g++.dg/abi/empty14.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty14a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty14.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty15.C b/gcc/testsuite/g++.dg/abi/empty15.C
index fd36194..2474911 100644
--- a/gcc/testsuite/g++.dg/abi/empty15.C
+++ b/gcc/testsuite/g++.dg/abi/empty15.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty15a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty15.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty16.C b/gcc/testsuite/g++.dg/abi/empty16.C
index 024b00e..6db82a2 100644
--- a/gcc/testsuite/g++.dg/abi/empty16.C
+++ b/gcc/testsuite/g++.dg/abi/empty16.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty16a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty16.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty17.C b/gcc/testsuite/g++.dg/abi/empty17.C
index a6e58fa..26f3d77 100644
--- a/gcc/testsuite/g++.dg/abi/empty17.C
+++ b/gcc/testsuite/g++.dg/abi/empty17.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty17a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty17.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty18.C b/gcc/testsuite/g++.dg/abi/empty18.C
index 6e64dae..02e41ca 100644
--- a/gcc/testsuite/g++.dg/abi/empty18.C
+++ b/gcc/testsuite/g++.dg/abi/empty18.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty18a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty18.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty19.C b/gcc/testsuite/g++.dg/abi/empty19.C
index 8707db8..89b92f1 100644
--- a/gcc/testsuite/g++.dg/abi/empty19.C
+++ b/gcc/testsuite/g++.dg/abi/empty19.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty19a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty19.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty22.C b/gcc/testsuite/g++.dg/abi/empty22.C
index d3720f8..1502ea0 100644
--- a/gcc/testsuite/g++.dg/abi/empty22.C
+++ b/gcc/testsuite/g++.dg/abi/empty22.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty22a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty22.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty25.C b/gcc/testsuite/g++.dg/abi/empty25.C
index 50a4c26..bfbaa83 100644
--- a/gcc/testsuite/g++.dg/abi/empty25.C
+++ b/gcc/testsuite/g++.dg/abi/empty25.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty25a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty25.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/g++.dg/abi/empty26.C b/gcc/testsuite/g++.dg/abi/empty26.C
index 785cdc7..3a27bf6 100644
--- a/gcc/testsuite/g++.dg/abi/empty26.C
+++ b/gcc/testsuite/g++.dg/abi/empty26.C
@@ -2,7 +2,7 @@
 // { dg-do run { target { { i?86-*-* x86_64-*-* } && { ! { ia32 } } } } }
 // { dg-options "-Wabi=11 -x c" }
 // { dg-additional-sources "empty26a.c" }
-// { dg-prune-output "command-line option" }
+// { dg-additional-options -Wno-complain-wrong-lang }
 
 #include "empty26.h"
 extern "C" void fun(struct dummy, struct foo);
diff --git a/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-1.c b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-1.c
new file mode 100644
index 0000000..71016e0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-1.c
@@ -0,0 +1,2 @@
+/* { dg-options -Wctad-maybe-unsupported } and '-Wcomplain-wrong-lang' enabled by default:
+   { dg-warning {command-line option '-Wctad-maybe-unsupported' is valid for C\+\+/ObjC\+\+ but not for C} {} { target *-*-* } 0 } */
diff --git a/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-2.c b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-2.c
new file mode 100644
index 0000000..ba2192d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-2.c
@@ -0,0 +1,2 @@
+/* { dg-options {-Wcomplain-wrong-lang -Wctad-maybe-unsupported} }
+   { dg-warning {command-line option '-Wctad-maybe-unsupported' is valid for C\+\+/ObjC\+\+ but not for C} {} { target *-*-* } 0 } */
diff --git a/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-3.c b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-3.c
new file mode 100644
index 0000000..36bf748
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-3.c
@@ -0,0 +1,2 @@
+/* { dg-options {-Wctad-maybe-unsupported -Wno-complain-wrong-lang} }
+   { dg-bogus {command-line option '-Wctad-maybe-unsupported' is valid for C\+\+/ObjC\+\+ but not for C} {} { target *-*-* } 0 } */
diff --git a/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-4.c b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-4.c
new file mode 100644
index 0000000..af185f8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-4.c
@@ -0,0 +1,2 @@
+/* { dg-options {-Wno-complain-wrong-lang -Wctad-maybe-unsupported} }
+   { dg-bogus {command-line option '-Wctad-maybe-unsupported' is valid for C\+\+/ObjC\+\+ but not for C} {} { target *-*-* } 0 } */
diff --git a/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-5.c b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-5.c
new file mode 100644
index 0000000..dc0a42c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wcomplain-wrong-lang-5.c
@@ -0,0 +1,2 @@
+/* { dg-options {-Wcomplain-wrong-lang -Wctad-maybe-unsupported -Wno-complain-wrong-lang} }
+   { dg-bogus {command-line option '-Wctad-maybe-unsupported' is valid for C\+\+/ObjC\+\+ but not for C} {} { target *-*-* } 0 } */
diff --git a/gcc/testsuite/gfortran.dg/bind-c-contiguous-1.f90 b/gcc/testsuite/gfortran.dg/bind-c-contiguous-1.f90
index 975f74b..d638dbb 100644
--- a/gcc/testsuite/gfortran.dg/bind-c-contiguous-1.f90
+++ b/gcc/testsuite/gfortran.dg/bind-c-contiguous-1.f90
@@ -1,7 +1,7 @@
 ! { dg-do run }
 ! { dg-additional-sources bind-c-contiguous-1.c }
 ! { dg-additional-options "-fcheck=all" }
-! { dg-prune-output "command-line option '-fcheck=.*' is valid for Fortran but not for C" }
+! { dg-additional-options -Wno-complain-wrong-lang }
 
 ! Fortran demands that with bind(C), the callee ensure that for
 ! * 'contiguous'
diff --git a/gcc/testsuite/gfortran.dg/bind-c-contiguous-4.f90 b/gcc/testsuite/gfortran.dg/bind-c-contiguous-4.f90
index a58ba20..591c5a7 100644
--- a/gcc/testsuite/gfortran.dg/bind-c-contiguous-4.f90
+++ b/gcc/testsuite/gfortran.dg/bind-c-contiguous-4.f90
@@ -4,7 +4,7 @@
 !
 ! { dg-additional-sources bind-c-contiguous-4.c }
 ! { dg-additional-options "-fcheck=all" }
-! { dg-prune-output "command-line option '-fcheck=.*' is valid for Fortran but not for C" }
+! { dg-additional-options -Wno-complain-wrong-lang }
 
 ! Fortran demands that with bind(C), the callee ensure that for
 ! * 'contiguous'
diff --git a/gcc/testsuite/gfortran.dg/bind-c-contiguous-5.f90 b/gcc/testsuite/gfortran.dg/bind-c-contiguous-5.f90
index d1af9f7..58d9a98 100644
--- a/gcc/testsuite/gfortran.dg/bind-c-contiguous-5.f90
+++ b/gcc/testsuite/gfortran.dg/bind-c-contiguous-5.f90
@@ -1,7 +1,7 @@
 ! { dg-do run }
 ! { dg-additional-sources bind-c-contiguous-5.c }
 ! { dg-additional-options "-fcheck=all" }
-! { dg-prune-output "command-line option '-fcheck=.*' is valid for Fortran but not for C" }
+! { dg-additional-options -Wno-complain-wrong-lang }
 !  ---- Same as bind-c-contiguous-1.f90 - but with kind=4 characters
 ! Fortran demands that with bind(C), the callee ensure that for
 ! * 'contiguous'
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 59be4fc..839e5a6 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -59,6 +59,10 @@ proc check_compile {basename type contents args} {
     } else {
 	set options ""
     }
+    # Silence "command-line option [...] is valid for [...] but not for [...]"
+    # that we may easily run into here, if more than one language is involved.
+    lappend options additional_flags=-Wno-complain-wrong-lang
+
     switch -glob -- $contents {
 	"*/\\* Assembly*" { set src ${basename}[pid].S }
 	"*! Fortran*" { set src ${basename}[pid].f90 }