Testsuite: Ensure stack protection is off for GCC

Using -fstack-protector-strong will cause GDB to break on the wrong line
when placing a breakpoint on a function.  This is due to inadequate dwarf
line numbering, and is being tracked by the GCC bug
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88432

GCC (and Clang) provided by Debian/Ubuntu default to stack protector
being enabled.

Ensure that when running the GDB testsuite, stack protector is always
turned off for GCC 4.1.0 (when stack protector was added) and above.

Ensure that this does not cause infinite recursion due to
test_compiler_info having to compile a file itself.

Add a test to explicitly test breakpoints with various levels of stack
protection on both GCC and Clang, with xfail for the known errors.

Restore change in ovldbreak.exp which worked around the issue.

gdb/testsuite/ChangeLog:

2019-01-18  Alan Hayward  <alan.hayward@arm.com>

	* gdb.base/stack-protector.c: New test.
	* gdb.base/stack-protector.exp: New file.
	* gdb.cp/ovldbreak.exp: Only allow a single break line.
	* lib/gdb.exp (get_compiler_info): Use getting_compiler_info
	option.
	(gdb_compile): Remove stack protector for GCC and prevent
	recursion.

1 files changed, 18 insertions, 2 deletions

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index ed9f89d..bc7ba12 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -3276,12 +3276,12 @@ proc get_compiler_info {{arg ""}} {
 	# We have to use -E and -o together, despite the comments
 	# above, because of how DejaGnu handles remote host testing.
 	set ppout "$outdir/compiler.i"
-	gdb_compile "${ifile}" "$ppout" preprocess [list "$arg" quiet]
+	gdb_compile "${ifile}" "$ppout" preprocess [list "$arg" quiet getting_compiler_info]
 	set file [open $ppout r]
 	set cppout [read $file]
 	close $file
     } else {
-	set cppout [ gdb_compile "${ifile}" "" preprocess [list "$arg" quiet] ]
+	set cppout [ gdb_compile "${ifile}" "" preprocess [list "$arg" quiet getting_compiler_info] ]
     }
     eval log_file $saved_log
 
@@ -3519,6 +3519,7 @@ proc gdb_compile {source dest type options} {
     }
     set shlib_found 0
     set shlib_load 0
+    set getting_compiler_info 0
     foreach opt $options {
         if {[regexp {^shlib=(.*)} $opt dummy_var shlib_name]
 	    && $type == "executable"} {
@@ -3549,11 +3550,26 @@ proc gdb_compile {source dest type options} {
             }
 	} elseif { $opt == "shlib_load" && $type == "executable" } {
 	    set shlib_load 1
+	} elseif { $opt == "getting_compiler_info" } {
+	    # If this is set, calling test_compiler_info will cause recursion.
+	    set getting_compiler_info 1
         } else {
             lappend new_options $opt
         }
     }
 
+    # Ensure stack protector is disabled for GCC, as this causes problems with
+    # DWARF line numbering.
+    # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88432
+    # This option defaults to on for Debian/Ubuntu.
+    if { $getting_compiler_info == 0
+	 && [test_compiler_info {gcc-*-*}]
+	 && !([test_compiler_info {gcc-[0-3]-*}]
+	      || [test_compiler_info {gcc-4-0-*}]) } {
+        # Put it at the front to not override any user-provided value.
+        lappend new_options "early_flags=-fno-stack-protector"
+    }
+
     # Because we link with libraries using their basename, we may need
     # (depending on the platform) to set a special rpath value, to allow
     # the executable to find the libraries it depends on.