build: update integer overflow sanitizer handling for fixed meson bugs

Change-Id: I27f33e66e107d4af13abe62257be8c696a6a6964

meson.build

@@ -43,6 +43,9 @@ project('lix', 'cpp', 'rust',
     'debug=true',
     'optimization=2',
     'errorlogs=true', # Please print logs for tests that fail
+    # Instead of using the default sanitizer, we combine this with
+    # -fsanitize-undefined-trap-on-error below in this file.
+    'b_sanitize=signed-integer-overflow',
   ],
 )
 
@@ -682,20 +685,15 @@ add_project_arguments(
   language : 'cpp',
 )
 
-# We turn off the production UBSan if the slower dev UBSan is requested, to
-# give better diagnostics.
-if cxx.get_id() in ['gcc', 'clang'] and 'undefined' not in get_option('b_sanitize')
-  # 2024-03-24: jade benchmarked the default sanitize reporting in clang and got
-  # a regression of about 10% on hackage-packages.nix with clang. So we are trapping instead.
-  #
-  # This has an unmeasurably low overhead in Nix evaluation benchmarks.
-  #
+# 2024-03-24: jade benchmarked the default sanitize reporting in clang and got
+# a regression of about 10% on hackage-packages.nix with clang. So if the
+# signed-integer-overflow sanitizer is requested (our default), we trap instead.
+# Trapping has an unmeasurably low overhead in Nix evaluation benchmarks.
+if cxx.get_id() in ['gcc', 'clang'] and 'signed-integer-overflow' in get_option('b_sanitize')
   # N.B. Meson generates a completely nonsense warning here:
   # https://github.com/mesonbuild/meson/issues/9822
-  # Both of these args cannot be written in the default meson configuration.
-  # b_sanitize=signed-integer-overflow is ignored, and
-  # -fsanitize-undefined-trap-on-error is not representable.
-  sanitize_args = ['-fsanitize=signed-integer-overflow', '-fsanitize-undefined-trap-on-error']
+  # -fsanitize-undefined-trap-on-error is not representable in -Db_sanitize=
+  sanitize_args = ['-fsanitize-undefined-trap-on-error']
   add_project_arguments(sanitize_args, language: 'cpp')
   add_project_link_arguments(sanitize_args, language: 'cpp')
 endif

package.nix

@@ -453,6 +453,7 @@ stdenv.mkDerivation (finalAttrs: {
     ++ lib.optionals hostPlatform.isStatic [
       "-Denable-embedded-sandbox-shell=true"
       "-Denable-contrib-plugins=false"
+      "-Db_sanitize=none"
     ]
     ++ lib.optional ciBuildAndDeleteBothLibraries "-Ddefault_library=both"
     # musl doesn't support fibers, and we can't detect this with meson alone.