treewide: Support builds with ASAN, enable in CI

Enables builds with ASAN to catch memory corruption
bugs faster and in CI. This is an incredibly valuable
instrument that must be used as much as possible.

Somewhat based on jade's work from Lix, though there's a lot that
we have to do differently:

19ae87e5ce

Co-authored-by: Jade Lovelace <lix@jade.fyi>

tests/functional/meson.build

@@ -239,6 +239,12 @@ foreach suite : suites
     # Turns, e.g., `tests/functional/flakes/show.sh` into a Meson test target called
     # `functional-flakes-show`.
     name = fs.replace_suffix(script, '')
+    asan_options = 'abort_on_error=1:print_summary=1:detect_leaks=0'
+    # Otherwise ASAN dumps warnings into stderr that make some tests fail on stderr output
+    # comparisons.
+    asan_options += ':log_path=@0@'.format(
+      meson.current_build_dir() / 'asan-log',
+    )
 
     test(
       name,
@@ -253,6 +259,7 @@ foreach suite : suites
       ],
       suite : suite_name,
       env : {
+        'ASAN_OPTIONS' : asan_options,
         '_NIX_TEST_SOURCE_DIR' : meson.current_source_dir(),
         '_NIX_TEST_BUILD_DIR' : meson.current_build_dir(),
         'TEST_NAME' : suite_name / name,

tests/functional/test-libstoreconsumer/main.cc

@@ -5,6 +5,13 @@
 
 using namespace nix;
 
+extern "C" [[gnu::retain]] const char * __asan_default_options()
+{
+    // We leak a bunch of memory knowingly on purpose. It's not worthwhile to
+    // diagnose that memory being leaked for now.
+    return "abort_on_error=1:print_summary=1:detect_leaks=0";
+}
+
 int main(int argc, char ** argv)
 {
     try {

tests/functional/test-libstoreconsumer/meson.build

@@ -1,3 +1,7 @@
+cxx = meson.get_compiler('cpp')
+
+subdir('nix-meson-build-support/asan-options')
+
 libstoreconsumer_tester = executable(
   'test-libstoreconsumer',
   'main.cc',

tests/functional/test-libstoreconsumer/nix-meson-build-support

@@ -0,0 +1 @@
+../../../nix-meson-build-support