[binutils-gdb] gdb.python/py-unwind: Disable stack protection

[Simon Marchi <simark at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=dcd27ddf875d6b913f1ddb0573c22b0931e36061

commit dcd27ddf875d6b913f1ddb0573c22b0931e36061
Author: Simon Marchi <simon.marchi@ericsson.com>
Date:   Sat Jul 22 00:01:03 2017 +0200

    gdb.python/py-unwind: Disable stack protection
    
    [I made some typo fixes but forgot to amend my commit before sending the patch,
     hence this v2.]
    
    I see the following failure on Ubuntu 16.04's gcc 5.4.0:
    
    Running /home/emaisin/src/binutils-gdb/gdb/testsuite/gdb.python/py-unwind.exp ...
    FAIL: gdb.python/py-unwind.exp: continue to breakpoint: break backtrace-broken
    FAIL: gdb.python/py-unwind.exp: Backtrace restored by unwinder (pattern 1)
    
    The problem is that the test expects a very particular stack layout.
    When stack protection is enabled, it adds a canary value which looks
    like an additional local variable.  This makes the test complain about
    a bad stack layout and fail.
    
    The simple solution is to disable stack protection for that test using
    -fno-stack-protector.  I checked older compilers (gcc 4.4, clang 3.5)
    and they support that flag, so I don't think it's necessary to probe for
    whether the compiler supports it.
    
    Maybe a better solution would be to change the test to make it cope with
    different stack layouts (perhaps it could save addresses of stuff in
    some global variables which GDB/the unwinder would read).  I'll go with
    the simple solution for now though.
    
    gdb/testsuite/ChangeLog:
    
    	* gdb.python/py-unwind.exp: Disable stack protection when
    	building test file.

Diff:
---
 gdb/testsuite/ChangeLog                | 5 +++++
 gdb/testsuite/gdb.python/py-unwind.exp | 7 ++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index eef141d..273d1f7 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-07-22  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* gdb.python/py-unwind.exp: Disable stack protection when
+	building test file.
+
 2017-07-20  Pedro Alves  <palves@redhat.com>
 
 	* gdb.base/default.exp (set language): Adjust expected output.
diff --git a/gdb/testsuite/gdb.python/py-unwind.exp b/gdb/testsuite/gdb.python/py-unwind.exp
index 625b04c..86e695c 100644
--- a/gdb/testsuite/gdb.python/py-unwind.exp
+++ b/gdb/testsuite/gdb.python/py-unwind.exp
@@ -20,7 +20,12 @@ load_lib gdb-python.exp
 
 standard_testfile
 
-if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
+# Stack protection can make the stack look a bit different, breaking the
+# assumptions this test has about its layout.
+
+set flags "additional_flags=-fno-stack-protector"
+
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} "debug $flags"] } {
     return -1
 }