[gdb/testsuite] Fix i386-mpx.exp compilation warnings

When running test-case gdb.arch/i386-mpx.exp with gcc-10, we get:
...
Running src/gdb/testsuite/gdb.arch/i386-mpx.exp ...
gdb compile failed, xgcc: warning: switch '-mmpx' is no longer supported
xgcc: warning: switch '-fcheck-pointer-bounds' is no longer supported
...

The test-case uses a combination of options, -mmpx and -fcheck-pointer-bounds.

The -fcheck-pointer-bounds option requires the -mmpx option:
...
$ gcc -fcheck-pointer-bounds ~/hello.c
hello.c:1:0: warning: Pointer Checker requires MPX support on this target. \
  Use -mmpx options to enable MPX.
 #include <stdio.h>

cc1: error: ‘-fcheck-pointer-bounds’ is not supported for this target
...

Both options is no longer supported in gcc-9.

Fix the warnings by testing if the option combination is supported.

Tested on x86_64-linux, with gcc-7.5.0 and gcc-10.0.1.

gdb/testsuite/ChangeLog:

2020-05-02  Tom de Vries  <tdevries@suse.de>

	* lib/gdb.exp (supports_mpx_check_pointer_bounds): New proc.
	* gdb.arch/i386-mpx-call.exp: Use supports_mpx_check_pointer_bounds.
	* gdb.arch/i386-mpx-map.exp: Same.
	* gdb.arch/i386-mpx-sigsegv.exp: Same.
	* gdb.arch/i386-mpx-simple_segv.exp: Same.
	* gdb.arch/i386-mpx.exp: Same.

7 files changed, 41 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index e741fd6..986e3be 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,14 @@
 2020-05-02  Tom de Vries  <tdevries@suse.de>
 
+	* lib/gdb.exp (supports_mpx_check_pointer_bounds): New proc.
+	* gdb.arch/i386-mpx-call.exp: Use supports_mpx_check_pointer_bounds.
+	* gdb.arch/i386-mpx-map.exp: Same.
+	* gdb.arch/i386-mpx-sigsegv.exp: Same.
+	* gdb.arch/i386-mpx-simple_segv.exp: Same.
+	* gdb.arch/i386-mpx.exp: Same.
+
+2020-05-02  Tom de Vries  <tdevries@suse.de>
+
 	* gdb.base/psym-external-decl.c (main): Add use of variable aaa.
 
 2020-05-01  Tom de Vries  <tdevries@suse.de>
diff --git a/gdb/testsuite/gdb.arch/i386-mpx-call.exp b/gdb/testsuite/gdb.arch/i386-mpx-call.exp
index b11adfc..41abbee 100644
--- a/gdb/testsuite/gdb.arch/i386-mpx-call.exp
+++ b/gdb/testsuite/gdb.arch/i386-mpx-call.exp
@@ -21,6 +21,10 @@ if { ![istarget i?86-*-*] && ![istarget x86_64-*-* ] } {
 
 standard_testfile
 
+if { ![supports_mpx_check_pointer_bounds] } {
+    return -1
+}
+
 set comp_flags "-mmpx -fcheck-pointer-bounds -I${srcdir}/../nat"
 
 if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
diff --git a/gdb/testsuite/gdb.arch/i386-mpx-map.exp b/gdb/testsuite/gdb.arch/i386-mpx-map.exp
index 3cde42f..995aaa1 100644
--- a/gdb/testsuite/gdb.arch/i386-mpx-map.exp
+++ b/gdb/testsuite/gdb.arch/i386-mpx-map.exp
@@ -23,6 +23,10 @@ if { ![istarget i?86-*-*] && ![istarget x86_64-*-* ] } {
 
 standard_testfile
 
+if { ![supports_mpx_check_pointer_bounds] } {
+    return -1
+}
+
 set comp_flags "-mmpx -fcheck-pointer-bounds -I${srcdir}/../nat/"
 
 if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
diff --git a/gdb/testsuite/gdb.arch/i386-mpx-sigsegv.exp b/gdb/testsuite/gdb.arch/i386-mpx-sigsegv.exp
index 72c9ec3..5e43f93 100644
--- a/gdb/testsuite/gdb.arch/i386-mpx-sigsegv.exp
+++ b/gdb/testsuite/gdb.arch/i386-mpx-sigsegv.exp
@@ -23,6 +23,10 @@ if { ![istarget i?86-*-*] && ![istarget x86_64-*-* ] } {
 
 standard_testfile
 
+if { ![supports_mpx_check_pointer_bounds] } {
+    return -1
+}
+
 set comp_flags "-mmpx -fcheck-pointer-bounds -I${srcdir}/../nat/"
 
 if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
diff --git a/gdb/testsuite/gdb.arch/i386-mpx-simple_segv.exp b/gdb/testsuite/gdb.arch/i386-mpx-simple_segv.exp
index 806d7d6..e707814 100644
--- a/gdb/testsuite/gdb.arch/i386-mpx-simple_segv.exp
+++ b/gdb/testsuite/gdb.arch/i386-mpx-simple_segv.exp
@@ -29,6 +29,10 @@ if { ![istarget i?86-*-*] && ![istarget x86_64-*-* ] } {
 
 standard_testfile
 
+if { ![supports_mpx_check_pointer_bounds] } {
+    return -1
+}
+
 set comp_flags "-mmpx -fcheck-pointer-bounds -I${srcdir}/../nat/"
 
 if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
diff --git a/gdb/testsuite/gdb.arch/i386-mpx.exp b/gdb/testsuite/gdb.arch/i386-mpx.exp
index 2cac70f..158550a 100644
--- a/gdb/testsuite/gdb.arch/i386-mpx.exp
+++ b/gdb/testsuite/gdb.arch/i386-mpx.exp
@@ -27,6 +27,10 @@ if { ![istarget i?86-*-*] && ![istarget x86_64-*-* ] } {
     return
 }
 
+if { ![supports_mpx_check_pointer_bounds] } {
+    return -1
+}
+
 set comp_flags "-mmpx -fcheck-pointer-bounds -I${srcdir}/../nat/"
 
 if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index b72ce0c..3732614 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -7007,6 +7007,18 @@ gdb_caching_proc supports_statement_frontiers {
     } executable "additional_flags=-gstatement-frontiers"]
 }
 
+# Return 1 if compiler supports -mmpx -fcheck-pointer-bounds.  Otherwise,
+# return 0.
+
+gdb_caching_proc supports_mpx_check_pointer_bounds {
+    set flags "additional_flags=-mmpx additional_flags=-fcheck-pointer-bounds"
+    return [gdb_can_simple_compile supports_mpx_check_pointer_bounds {
+	int main () {
+	    return 0;
+	}
+    } executable $flags]
+}
+
 # Return 1 if symbols were read in using -readnow.  Otherwise, return 0.
 
 proc readnow { } {