From 81bda366b3073bd46e80052d03c081e390a04094 Mon Sep 17 00:00:00 2001
From: Andrew Jackson <andrew.jackson@supabase.io>
Date: Sat, 24 Oct 2026 23:14:25 -0500
Subject: [PATCH 1/2] feat: add UBSAN/ASAN

---
 .github/workflows/ci.yml   | 29 ++++++++++++++++++++++++++++-
 examples/hello/src/hello.c | 13 +++++++++++++
 nix/postgresql/generic.nix | 17 ++++++++++++-----
 nix/xpg.nix                | 20 +++++++++++++++-----
 4 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 43bf43e..971292c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -76,9 +76,18 @@ jobs:
 
       - name: Install GCC
         run: |
-          nix profile install nixpkgs#gcc14
+          nix profile install nixpkgs#gcc15
           echo "$HOME/.nix-profile/bin" >> "$GITHUB_PATH"
 
+      # TODO: Currently builds are not fully hermetic. We will care about the state of the machine 
+      #       until we can invest in making this repo fully hermetic
+      - name: Print state
+        run: |
+          gcc --version
+          ulimit -s
+          cat /etc/os-release
+          which gcc
+
       - name: Build postgres extension
         run: |
           cd examples/hello
@@ -96,13 +105,31 @@ jobs:
           nix run .#xpg${{ matrix.pg-version }} -- --options "-c work_mem=8MB" psql -c "DO \$\$ BEGIN ASSERT current_setting('work_mem') = '8MB'; END \$\$;"
 
           # test for cassert enabled build
+          rm -rf build-${{ matrix.pg-version }}
           nix run .#xpg${{ matrix.pg-version }} -- --cassert psql -c "DO \$\$ BEGIN ASSERT current_setting('debug_assertions') = 'on'; END \$\$;"
 
           # test for pg core test
+          rm -rf ./build-{{ matrix.pg-version }}
           if [ "${{ matrix.pg-version }}" -ge 15 ]; then
             nix run .#xpg${{ matrix.pg-version }} -- test-core
           fi
 
+      - name: Test UBSAN reporting
+        run: |
+          cd examples/hello
+          rm -rf ./build-{{ matrix.pg-version }}
+
+          # run test with cassert and injected DIV_BY_ZERO error, print all stdout but exit non zero if 
+          # expected error code not found
+          (HELLO_NULL_PTR_DEREF=1 nix run .#xpg${{ matrix.pg-version }} -- --cassert -v ${{ matrix.pg-version }} test 2>&1 || true) | awk '/runtime error: load of null pointer of type/ { found=1 } { print } END { if (!found) exit 1 }'
+
+      - name: Test ASAN reporting
+        run: |
+          cd examples/hello
+          # run test with cassert and injected OOB_WRITE error, print all stdout but exit non zero if 
+          # expected error code not found
+          (HELLO_OOB_WRITE=1 nix run .#xpg${{ matrix.pg-version }} -- --cassert -v ${{ matrix.pg-version }} test 2>&1 || true) | awk '/SUMMARY: AddressSanitizer: heap-buffer-overflow/  { found=1 } { print } END { if (!found) exit 1 }'
+
       - if: ${{ failure() }}
         run: |
           cd examples/hello
diff --git a/examples/hello/src/hello.c b/examples/hello/src/hello.c
index df29c7e..a7b7714 100644
--- a/examples/hello/src/hello.c
+++ b/examples/hello/src/hello.c
@@ -9,6 +9,19 @@ Datum hello(PG_FUNCTION_ARGS){
   StringInfoData buf;
   initStringInfo(&buf);
 
+  // ASAN should flag this
+  if (getenv("HELLO_OOB_WRITE")) {
+    char *buf2 = (char *)malloc(4);
+    buf2[5] = 'A'; // Writing past the 4-byte heap buffer
+    free(buf2);
+  }
+ 
+  // UBSAN should flag this
+  if (getenv("HELLO_NULL_PTR_DEREF")) {
+    int *i = NULL;
+    printf("%d\n", *i);
+  }
+
   appendStringInfoString(&buf, "hello ");
   appendBinaryStringInfo(&buf, VARDATA_ANY(input), VARSIZE_ANY_EXHDR(input));
 
diff --git a/nix/postgresql/generic.nix b/nix/postgresql/generic.nix
index 7065bd8..09adcc8 100644
--- a/nix/postgresql/generic.nix
+++ b/nix/postgresql/generic.nix
@@ -142,6 +142,12 @@ let
 
       buildFlags = [ "world" ];
 
+      env.CFLAGS =
+        ""
+        + lib.optionalString cassertSupport "-fsanitize=undefined -fno-sanitize-recover=all -fno-omit-frame-pointer "
+        + lib.optionalString (cassertSupport && stdenv.isDarwin) "-fno-sanitize=function"
+        + lib.optionalString (cassertSupport && stdenv'.isLinux) "-fsanitize=address";
+
       # Makes cross-compiling work when xml2-config can't be executed on the host.
       # Fixed upstream in https://github.com/postgres/postgres/commit/0bc8cebdb889368abdf224aeac8bc197fe4c9ae6
       env.NIX_CFLAGS_COMPILE =
@@ -300,11 +306,12 @@ let
       # autodetection doesn't seem to able to find this, but it's there.
       checkTarget = "check";
 
-      # PG 19+ embeds additional tool paths in installed artifacts, so keep the
-      # stricter gcc-wrapper reference check only for older versions for now.
-      disallowedReferences = lib.optionals (lib.versionOlder (lib.versions.major version) "19") [
-        stdenv'.cc
-      ];
+      # Prevents hardcoded file paths referencing nix store in pg19
+      disallowedReferences =
+        lib.optionals (lib.versionOlder (lib.versions.major version) "19" && !cassertSupport)
+          [
+            stdenv'.cc
+          ];
 
       passthru =
         let
diff --git a/nix/xpg.nix b/nix/xpg.nix
index fd0b131..629585d 100644
--- a/nix/xpg.nix
+++ b/nix/xpg.nix
@@ -52,11 +52,21 @@ let
       ${
         if cassert then
           ''
-            if [ "$_arg_cassert" = on ]; then
-              export PATH=${ourPg."postgresql_${v}_cassert"}/bin:"$PATH"
-            else
-              export PATH=${ourPg."postgresql_${v}"}/bin:"$PATH"
-            fi
+                      if [ "$_arg_cassert" = on ]; then
+                        export PATH=${ourPg."postgresql_${v}_cassert"}/bin:"$PATH"
+
+                        # See below links
+                        # TODO: detect_stack_use_after_return in ASAN_OPTIONS can be removed after 
+                        #       below patch lands and is backported, thought it will still need to 
+                        #       remain for EOL'd versions
+                        # https://www.postgresql.org/message-id/flat/2kk4z4odvuyrg7qlwjd7ft4eron4cle4btb33v4qatgsdkayir%40gj6e62rgsel4
+                        # https://github.com/postgres/postgres/blob/51ae21aa313bb6b79ad914920279cd0d89e92220/.github/workflows/pg-ci.yml#L464
+
+            	        export UBSAN_OPTIONS="print_stacktrace=1:disable_coredump=0:abort_on_error=1:verbosity=2"
+            	        export ASAN_OPTIONS="print_stacktrace=1:disable_coredump=0:abort_on_error=1:detect_leaks=0:detect_stack_use_after_return=0"
+                      else
+                        export PATH=${ourPg."postgresql_${v}"}/bin:"$PATH"
+                      fi
           ''
         else
           ''

From 8d0158151edf83b560de1e694209eec589ea0f4b Mon Sep 17 00:00:00 2001
From: Your Name <you@example.com>
Date: Fri, 30 Oct 2026 19:02:00 +0000
Subject: [PATCH 2/2] docs: add notes

---
 nix/postgresql/generic.nix | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/nix/postgresql/generic.nix b/nix/postgresql/generic.nix
index 09adcc8..ed64e16 100644
--- a/nix/postgresql/generic.nix
+++ b/nix/postgresql/generic.nix
@@ -146,6 +146,9 @@ let
         ""
         + lib.optionalString cassertSupport "-fsanitize=undefined -fno-sanitize-recover=all -fno-omit-frame-pointer "
         + lib.optionalString (cassertSupport && stdenv.isDarwin) "-fno-sanitize=function"
+        # TODO: compiling with clang on darwin with -fsanitize=address results in a binary
+        #       that never returns and pins at 100% CPU saturation of a single core. Possibly
+        #       revisit the below if this ever gets fixed
         + lib.optionalString (cassertSupport && stdenv'.isLinux) "-fsanitize=address";
 
       # Makes cross-compiling work when xml2-config can't be executed on the host.