Avoid timeouts in gdb.compile

PR compile/29541 points out that some of the C++ tests in gdb.compile
will time out when the glibc debuginfo is installed.  This was
interfering with my hacking on gdb by making test runs extremely long,
so I looked into it.

Internally the bug seems to be that gdb tries to convert multiple
symbols named "var" via the compiler interface; one such symbol (I
didn't track it down too far) causes the C++ compiler plugin to crash.

Unfortunately, the crash is reported as a timeout, as the gdb side of
the plugin simply hangs.  This seems like a bug in the plugin RPC
mechanism and, worse, apparently when I wrote this stuff I didn't
really consider error reporting very much at all, so gdb can't really
detect failures in the first place.

Anyway... this patch works around the timeout by compiling a simple
test that should provoke this bug, and then using "untested" if it
notices a GCC crash.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29541

gdb/testsuite/gdb.compile/compile-cplus-anonymous.exp

@@ -33,15 +33,13 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
-    return -1
-}
-
 gdb_breakpoint [gdb_get_line_number "break here" $srcfile]
 gdb_continue_to_breakpoint "testing location"
 
+if {[skip_compile_feature_untested "var = 0"]} {
+    return -1
+}
+
 # Reminder, "var" is an integer; all these types get converted to `int'.
 CompileExpression::new "var"
 CompileExpression::test "anon_e" {(3|GHI)}

gdb/testsuite/gdb.compile/compile-cplus-array-decay.exp

@@ -33,9 +33,7 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
+if {[skip_compile_feature_untested]} {
     return -1
 }
 

gdb/testsuite/gdb.compile/compile-cplus-inherit.exp

@@ -33,15 +33,13 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
-    return -1
-}
-
 gdb_breakpoint [gdb_get_line_number "break here" $srcfile]
 gdb_continue_to_breakpoint "testing location"
 
+if {[skip_compile_feature_untested "var = 0"]} {
+    return -1
+}
+
 CompileExpression::new "var"
 CompileExpression::test "d.a_" 1
 CompileExpression::test "d.b_" 2

gdb/testsuite/gdb.compile/compile-cplus-member.exp

@@ -33,15 +33,13 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
-    return -1
-}
-
 gdb_breakpoint [gdb_get_line_number "break here" $srcfile]
 gdb_continue_to_breakpoint "testing location"
 
+if {[skip_compile_feature_untested "var = 0"]} {
+    return -1
+}
+
 CompileExpression::new "var"
 CompileExpression::test "a.public_" 1
 CompileExpression::test "a.protected_" {(21|N::NB)}

gdb/testsuite/gdb.compile/compile-cplus-method.exp

@@ -33,15 +33,13 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
-    return -1
-}
-
 gdb_breakpoint [gdb_get_line_number "break here" $srcfile]
 gdb_continue_to_breakpoint "testing location"
 
+if {[skip_compile_feature_untested "var = 0"]} {
+    return -1
+}
+
 CompileExpression::new "var"
 CompileExpression::test "a->get_var ()" 21
 CompileExpression::test "a->get_var (static_cast<unsigned long> (1))" 100

gdb/testsuite/gdb.compile/compile-cplus-namespace.exp

@@ -33,15 +33,13 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
-    return -1
-}
-
 gdb_breakpoint [gdb_get_line_number "break here" $srcfile]
 gdb_continue_to_breakpoint "testing location"
 
+if {[skip_compile_feature_untested "var = 0"]} {
+    return -1
+}
+
 CompileExpression::new "var"
 CompileExpression::test "N1::N2::N3::N4::n4static" 400
 CompileExpression::test "N1::N2::N3::N4::S4::s4static" 40

gdb/testsuite/gdb.compile/compile-cplus-nested.exp

@@ -33,15 +33,13 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
-    return -1
-}
-
 gdb_breakpoint [gdb_get_line_number "break here" $srcfile]
 gdb_continue_to_breakpoint "testing location"
 
+if {[skip_compile_feature_untested "var = 0"]} {
+    return -1
+}
+
 CompileExpression::new "var"
 CompileExpression::test "i1.a_" 2
 CompileExpression::test "i2.a_" 3

gdb/testsuite/gdb.compile/compile-cplus-print.exp

@@ -36,8 +36,7 @@ if ![runto_main] {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested "compile command not supported (could not find libcc1 shared library?)"
+if {[skip_compile_feature_untested]} {
     return -1
 }
 

gdb/testsuite/gdb.compile/compile-cplus-virtual.exp

@@ -33,15 +33,13 @@ if {![runto_main]} {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested \
-	"compile command not supported (could not find libcc1 shared library?)"
-    return -1
-}
-
 gdb_breakpoint [gdb_get_line_number "break here" $srcfile]
 gdb_continue_to_breakpoint "testing location"
 
+if {[skip_compile_feature_untested "var = 0"]} {
+    return -1
+}
+
 CompileExpression::new "var"
 CompileExpression::test "b.doit ()" 2
 CompileExpression::test "c.doit ()" 3

gdb/testsuite/gdb.compile/compile-cplus.exp

@@ -52,8 +52,10 @@ if ![runto_main] {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested "compile command not supported (could not find libcc1 shared library?)"
+gdb_breakpoint [gdb_get_line_number "break-here"]
+gdb_continue_to_breakpoint "break-here" ".* break-here .*"
+
+if {[skip_compile_feature_untested "var = 0"]} {
     return -1
 }
 
@@ -132,9 +134,6 @@ gdb_test "compile code *(volatile int *) 0 = 0;" \
     "The program being debugged was signaled while in a function called from GDB\\.\r\nGDB has restored the context to what it was before the call\\.\r\n.*" \
     "compile code segfault second"
 
-gdb_breakpoint [gdb_get_line_number "break-here"]
-gdb_continue_to_breakpoint "break-here" ".* break-here .*"
-
 # C++ Specific tests.
 ## Public methods and members
 

gdb/testsuite/gdb.compile/compile-ifunc.exp

@@ -43,8 +43,7 @@ with_test_prefix "nodebug" {
     # feature check below will work.
     gdb_test_no_output "set language c" ""
 
-    if {[skip_compile_feature_tests]} {
-	untested "compile command not supported (could not find libcc1 shared library?)"
+    if {[skip_compile_feature_untested]} {
 	return -1
     }
 

gdb/testsuite/gdb.compile/compile-ops.exp

@@ -418,8 +418,7 @@ if ![runto func] {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested "compile command not supported (could not find libcc1 shared library?)"
+if {[skip_compile_feature_untested]} {
     return -1
 }
 

gdb/testsuite/gdb.compile/compile-print.exp

@@ -25,8 +25,7 @@ if ![runto_main] {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested "compile command not supported (could not find libcc1 shared library?)"
+if {[skip_compile_feature_untested]} {
     return -1
 }
 

gdb/testsuite/gdb.compile/compile-setjmp.exp

@@ -25,8 +25,7 @@ if ![runto_main] {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested "compile command not supported (could not find libcc1 shared library?)"
+if {[skip_compile_feature_untested]} {
     return -1
 }
 

gdb/testsuite/gdb.compile/compile-tls.exp

@@ -27,8 +27,7 @@ if {![runto_main]} {
    return 0
 }
 
-if {[skip_compile_feature_tests]} {
-    untested "compile command not supported (could not find libcc1 shared library?)"
+if {[skip_compile_feature_untested]} {
     return -1
 }
 

gdb/testsuite/gdb.compile/compile.exp

@@ -57,8 +57,7 @@ if ![runto_main] {
     return -1
 }
 
-if {[skip_compile_feature_tests]} {
-    untested "compile command not supported (could not find libcc1 shared library?)"
+if {[skip_compile_feature_untested]} {
     return -1
 }
 

gdb/testsuite/lib/compile-support.exp

@@ -15,16 +15,31 @@
 
 # Generic/oft used support routines for testing GDB's compile feature.
 
-# Return 1 if we should skip tests of the "compile" feature.
-# This must be invoked after the inferior has been started.
+# Helper function for skip_compile_feature_tests.  This does the real
+# work, but should not be called directly.  Returns a failure reason
+# (a string) on failure, or the empty string on success.
 
-proc skip_compile_feature_tests {} {
+proc _do_check_compile {expr} {
     global gdb_prompt
 
-    set result 0
-    gdb_test_multiple "compile code -- ;" "check for working compile command" {
+    set result ""
+    gdb_test_multiple "compile code -- $expr;" "check for working compile command" {
 	"Could not load libcc1.*\r\n$gdb_prompt $" {
-	    set result 1
+	    set result "could not find libcc1"
+	}
+	"Could not load libcp1.*\r\n$gdb_prompt $" {
+	    set result "could not find libcp1"
+	}
+	-re "WARNING .* there are active plugins, do not report this" {
+	    # Note that the regexp above does not check for the
+	    # prompt.  This avoids a gratuitous timeout.
+	    set result "GCC crashed"
+	}
+	-re "confused by earlier errors, bailing out" {
+	    # This scenario can happen when either GCC or GDB is
+	    # confused by some other debuginfo.
+	    # See PR compile/29541.
+	    set result "confused by glibc debuginfo"
 	}
 	-re "\r\n$gdb_prompt $" {
 	}
@@ -32,6 +47,27 @@ proc skip_compile_feature_tests {} {
     return $result
 }
 
+# Return 1 if we should skip tests of the "compile" feature.
+# This must be invoked after the inferior has been started.
+# EXPR is the expression to test, if any (using the default empty EXPR
+# works fine in most cases).
+
+proc skip_compile_feature_tests {{expr ""}} {
+    return [expr {[string length [_do_check_compile $expr]] > 0}]
+}
+
+# Like skip_compile_feature_tests, but also issue an "untested" when
+# skipping.
+
+proc skip_compile_feature_untested {{expr ""}} {
+    set output [_do_check_compile $expr]
+    if {[string length $output] > 0} {
+	untested "compile command not supported ($output)"
+	return 1
+    }
+    return 0
+}
+
 # This namespace provides some convenience functions for running
 # "compile code" and "compile print" tests.
 #