[PATCH] Disable the undefined behavior sanitizer by default

Tom Tromey
2018-10-09T18:02:38Z

There have been a few undefined behavior failures reported, and Pedro
suggested that the sanitizer be disabled by default. This patch
implements this.

gdb/ChangeLog
2018-10-09 Tom Tromey <tom@tromey.com>

* configure: Rebuild.
* sanitize.m4 (AM_GDB_UBSAN): Default to no.
* NEWS: Update --enable-ubsan documentation.

gdb/doc/ChangeLog
2018-10-09 Tom Tromey <tom@tromey.com>

* gdb.texinfo (Configure Options): Update --enable-ubsan
documentation.
---
gdb/ChangeLog | 6 ++++++
gdb/NEWS | 10 +++++-----
gdb/configure | 2 +-
gdb/doc/ChangeLog | 5 +++++
gdb/doc/gdb.texinfo | 13 +++++++------
gdb/sanitize.m4 | 2 +-
6 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 8a0dd52fa7..126e61e282 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -122,11 +122,11 @@ FreeBSD/riscv riscv*-*-freebsd*

--enable-ubsan

- Enable or disable the undefined behavior sanitizer. Release
- versions of GDB disable this by default if it is available, but
- development versions enable it. Enabling this can cause a
- performance penalty. The undefined behavior sanitizer was first
- introduced in GCC 4.9.
+ Enable or disable the undefined behavior sanitizer. This is
+ disabled by default, but passing --enable-ubsan=yes or
+ --enable-ubsan=auto to configure will enable it. Enabling this can
+ cause a performance penalty. The undefined behavior sanitizer was
+ first introduced in GCC 4.9.

*** Changes in GDB 8.2

diff --git a/gdb/configure b/gdb/configure
index 304adc81fe..adb26e5d4d 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -15614,7 +15614,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
if test "${enable_ubsan+set}" = set; then :
enableval=$enable_ubsan;
else
- enable_ubsan=auto
+ enable_ubsan=no
fi

if test "x$enable_ubsan" = xauto; then
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index efd6dffb1e..b0dc3bf67c 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35771,12 +35771,13 @@ to the compiler, which will fail the compilation if the compiler
outputs any warning messages.

@item --enable-ubsan
-Enable the GCC undefined behavior sanitizer. By default this is
-disabled in @value{GDBN} releases, but enabled, when available, when
-building from git. The undefined behavior sanitizer checks for
-C@t{++} undefined behavior. It has a performance cost, so if you are
-looking at @value{GDBN}'s performance, you should disable it. The
-undefined behavior sanitizer was first introduced in GCC 4.9.
+Enable the GCC undefined behavior sanitizer. This is disabled by
+default, but passing @code{--enable-ubsan=yes} or
+@code{--enable-ubsan=auto} to @code{configure} will enable it. The
+undefined behavior sanitizer checks for C@t{++} undefined behavior.
+It has a performance cost, so if you are looking at @value{GDBN}'s
+performance, you should disable it. The undefined behavior sanitizer
+was first introduced in GCC 4.9.
@end table

@node System-wide configuration
diff --git a/gdb/sanitize.m4 b/gdb/sanitize.m4
index 76df44da4f..979f6461c0 100644
--- a/gdb/sanitize.m4
+++ b/gdb/sanitize.m4
@@ -20,7 +20,7 @@ AC_DEFUN([AM_GDB_UBSAN],[
AC_ARG_ENABLE(ubsan,
AS_HELP_STRING([--enable-ubsan],
[enable undefined behavior sanitizer (auto/yes/no)]),
- [],enable_ubsan=auto)
+ [],enable_ubsan=no)
if test "x$enable_ubsan" = xauto; then
if $development; then
enable_ubsan=yes
--
2.17.1