From 6894c964f3504ab2bc09b46e17ba30c725d232f3 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Tue, 14 Oct 2025 11:19:16 +0100
Subject: [PATCH 1/2] Fix Clang 21+ `-Wuninitialized-const-pointer` warning
 when using MSan

Co-authored-by: Tim Ruffing <me@real-or-random.org>
---
 src/checkmem.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/checkmem.h b/src/checkmem.h
index 7e333ce5f3..08eae47d78 100644
--- a/src/checkmem.h
+++ b/src/checkmem.h
@@ -48,7 +48,17 @@
 #  if __has_feature(memory_sanitizer)
 #    include <sanitizer/msan_interface.h>
 #    define SECP256K1_CHECKMEM_ENABLED 1
-#    define SECP256K1_CHECKMEM_UNDEFINE(p, len) __msan_allocated_memory((p), (len))
+#    if defined(__clang__) && ((__clang_major__ == 21 && __clang_minor__ >= 1) || __clang_major__ >= 22)
+#      define SECP256K1_CHECKMEM_UNDEFINE(p, len) do { \
+         /* Work around https://github.com/llvm/llvm-project/issues/160094 */ \
+         _Pragma("clang diagnostic push") \
+         _Pragma("clang diagnostic ignored \"-Wuninitialized-const-pointer\"") \
+         __msan_allocated_memory((p), (len)); \
+         _Pragma("clang diagnostic pop") \
+         } while(0)
+#    else
+#      define SECP256K1_CHECKMEM_UNDEFINE(p, len) __msan_allocated_memory((p), (len))
+#    endif
 #    define SECP256K1_CHECKMEM_DEFINE(p, len) __msan_unpoison((p), (len))
 #    define SECP256K1_CHECKMEM_MSAN_DEFINE(p, len) __msan_unpoison((p), (len))
 #    define SECP256K1_CHECKMEM_CHECK(p, len) __msan_check_mem_is_initialized((p), (len))

From 53585f93b7e6fe3933c77216f45e7d4f785436b5 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Tue, 14 Oct 2025 11:19:45 +0100
Subject: [PATCH 2/2] ci: Use clang-snapshot in "MSan" job

---
 .github/workflows/ci.yml   | 5 ++++-
 ci/linux-debian.Dockerfile | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f22ef2a3c0..ad3568d1ea 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -417,6 +417,9 @@ jobs:
               # when ctime_tests when enabled.
               CFLAGS: '-fsanitize=memory -fsanitize-recover=memory -fsanitize-memory-param-retval -g'
               CTIMETESTS: 'no'
+        cc:
+          - 'clang'
+          - 'clang-snapshot'
 
     env:
       ECDH: 'yes'
@@ -425,7 +428,7 @@ jobs:
       SCHNORRSIG: 'yes'
       MUSIG: 'yes'
       ELLSWIFT: 'yes'
-      CC: 'clang'
+      CC: ${{ matrix.cc }}
       SECP256K1_TEST_ITERS: 32
       ASM: 'no'
       WITH_VALGRIND: 'no'
diff --git a/ci/linux-debian.Dockerfile b/ci/linux-debian.Dockerfile
index 22b6d35c92..a575d9b1c4 100644
--- a/ci/linux-debian.Dockerfile
+++ b/ci/linux-debian.Dockerfile
@@ -71,7 +71,7 @@ RUN \
     # Determine the version number of the LLVM development branch
     LLVM_VERSION=$(apt-cache search --names-only '^clang-[0-9]+$' | sort -V | tail -1 | cut -f1 -d" " | cut -f2 -d"-" ) && \
     # Install
-    DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y "clang-${LLVM_VERSION}" && \
+    DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y "clang-${LLVM_VERSION}" "libclang-rt-${LLVM_VERSION}-dev" && \
     # Create symlink
     ln -s "/usr/bin/clang-${LLVM_VERSION}" /usr/bin/clang-snapshot && \
     # Clean up