mtest: set ASAN_OPTIONS and UBSAN_OPTIONS to abort by default

Do as we do for MALLOC_PERTURB and set a sensible value for both ASAN_OPTIONS
and UBSAN_OPTIONS to abort on failure and give more helpful output at the
same time. We do not set these options if the user has exported a value
themselves to allow override.

In the last week alone, I've observed two cases where people were expecting
sanitizers to abort on failure and were surprised when it didn't:
1) https://github.com/git/git/commit/252d693797912ddb2684733160170f0408b73274
2) https://gitlab.freedesktop.org/pipewire/pipewire/-/commit/c47df433f7bc9936fc59b323ca5e53ea4a04f40e

Correct this - which is in-line with meson's DWIM/DTRT philosophy.

Signed-off-by: Sam James <sam@gentoo.org>

4 files changed, 24 insertions, 0 deletions

diff --git a/docs/markdown/Unit-tests.md b/docs/markdown/Unit-tests.md
index 030eb19..7ad95d2 100644
--- a/docs/markdown/Unit-tests.md
+++ b/docs/markdown/Unit-tests.md
@@ -38,6 +38,12 @@ set to a random value between 1..255. This can help find memory leaks on
 configurations using glibc, including with non-GCC compilers. This feature
 can be disabled as discussed in [[test]].
 
+### ASAN_OPTIONS and UBSAN_OPTIONS
+
+By default, the environment variables `ASAN_OPTIONS` and `UBSAN_OPTIONS` are
+set to enable aborting on detected violations and to give a backtrace. This
+feature can be disabled as discussed in [[test]].
+
 ## Coverage
 
 If you enable coverage measurements by giving Meson the command line
diff --git a/docs/markdown/snippets/sanitizers_test.md b/docs/markdown/snippets/sanitizers_test.md
new file mode 100644
index 0000000..2492911
--- /dev/null
+++ b/docs/markdown/snippets/sanitizers_test.md
@@ -0,0 +1,5 @@
+## Tests now abort on errors by default under sanitizers
+
+Sanitizers like AddressSanitizer and UndefinedBehaviorSanitizer do not abort
+by default on detected violations. Meson now exports `ASAN_OPTIONS` and `UBSAN_OPTIONS`
+when unset in the environment to provide sensible abort-by-default behavior.
diff --git a/docs/yaml/functions/test.yaml b/docs/yaml/functions/test.yaml
index 4e79167..622b7c3 100644
--- a/docs/yaml/functions/test.yaml
+++ b/docs/yaml/functions/test.yaml
@@ -33,6 +33,10 @@ description: |
   test(..., env: nomalloc, ...)
   ```
 
+  By default, the environment variables `ASAN_OPTIONS` and `UBSAN_OPTIONS` are
+  set to enable aborting on detected violations and to give a backtrace. To suppress
+  this, `ASAN_OPTIONS` and `UBSAN_OPTIONS` can be set in the environment.
+
   In addition to running individual executables as test cases, `test()`
   can also be used to invoke an external test harness.  In this case,
   it is best to use `verbose: true` *(since 0.62.0)* and, if supported
diff --git a/mesonbuild/mtest.py b/mesonbuild/mtest.py
index 1298cc0..291b1e2 100644
--- a/mesonbuild/mtest.py
+++ b/mesonbuild/mtest.py
@@ -1418,6 +1418,15 @@ class SingleTestRunner:
         if ('MALLOC_PERTURB_' not in env or not env['MALLOC_PERTURB_']) and not options.benchmark:
             env['MALLOC_PERTURB_'] = str(random.randint(1, 255))
 
+        # Sanitizers do not default to aborting on error. This is counter to
+        # expectations when using -Db_sanitize and has led to confusion in the wild
+        # in CI. Set our own values of {ASAN,UBSAN}_OPTOINS to rectify this, but
+        # only if the user has not defined them.
+        if ('ASAN_OPTIONS' not in env or not env['ASAN_OPTIONS']):
+            env['ASAN_OPTIONS'] = 'halt_on_error=1:abort_on_error=1:print_summary=1'
+        if ('UBSAN_OPTIONS' not in env or not env['UBSAN_OPTIONS']):
+            env['UBSAN_OPTIONS'] = 'halt_on_error=1:abort_on_error=1:print_summary=1:print_stacktrace=1'
+
         if self.options.gdb or self.test.timeout is None or self.test.timeout <= 0:
             timeout = None
         elif self.options.timeout_multiplier is None: