Merge changes from topic "undefined-behaviour" into main

* changes:
  releng: move officialRelease to version.json
  Add -Werror CI job
  ci: add a asan+ubsan test run on x86_64-linux
  tree-wide: add support for asan!

src/asan-options/asan-options.cc

@@ -0,0 +1,17 @@
+/// @file This is very bothersome code that has to be included in every
+/// executable to get the correct default ASan options. I am so sorry.
+
+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.
+    //
+    // Instruction bytes are useful for finding the actual code that
+    // corresponds to an ASan report.
+    //
+    // TODO: setting log_path=asan.log or not: neither works, since you can't
+    // write to the fs in certain places in the testsuite, but you also cannot
+    // write arbitrarily to stderr in other places so the reports get eaten.
+    // pain 🥖
+    return "halt_on_error=1:abort_on_error=1:detect_leaks=0:print_summary=1:dump_instruction_bytes=1";
+}

src/meson.build

@@ -12,10 +12,19 @@ subdir('libmain')
 # libcmd depends on everything
 subdir('libcmd')
 
-
 # The rest of the subdirectories aren't separate components,
 # just source files in another directory, so we process them here.
 
+# Static library that just sets default ASan options. It needs to be included
+# in every executable.
+asanoptions = static_library(
+  'libasanoptions',
+  files('asan-options/asan-options.cc'),
+)
+libasanoptions = declare_dependency(
+  link_whole: asanoptions
+)
+
 build_remote_sources = files(
   'build-remote/build-remote.cc',
 )

src/nix/meson.build

@@ -80,6 +80,7 @@ nix = executable(
   profiles_md_gen,
   nix2_commands_sources,
   dependencies : [
+    libasanoptions,
     liblixcmd,
     liblixutil_mstatic,
     liblixstore_mstatic,