fix: suppress deprecated-literal-operator error on Apple Clang 21+

.github/actions/setup-cvc5/action.yml

@@ -29,6 +29,30 @@ runs:
         path: cvc5-sys/cvc5/build
         key: ${{ runner.os }}-cvc5-${{ hashFiles('cvc5-sys/cvc5/**/*.cmake', 'cvc5-sys/cvc5/CMakeLists.txt') }}
 
+    - name: Patch FindPoly.cmake for Apple Clang 21+
+      if: steps.cache-static.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        # Apple Clang 21+ (macOS 26+) errors on the deprecated
+        # whitespace-before-suffix syntax in gmpxx.h literal operators.
+        # libpoly builds with -Werror, so the warning becomes fatal.
+        # The existing cmake only suppresses this for WASM builds;
+        # make it unconditional using the strong -Wno- form.
+        # See https://github.com/cvc5/cvc5-rs/issues/56
+        F=cvc5-sys/cvc5/cmake/FindPoly.cmake
+        python3 -c "
+        import pathlib, sys
+        f = pathlib.Path('$F')
+        if not f.exists():
+            sys.exit(0)
+        t = f.read_text()
+        old = 'set(POLY_CXX_FLAGS \"\")\n  if(NOT(WASM STREQUAL \"OFF\"))\n    set(POLY_CXX_FLAGS -DCMAKE_CXX_FLAGS=-Wno-error=deprecated-literal-operator)\n  endif()'
+        new = 'set(POLY_CXX_FLAGS -DCMAKE_CXX_FLAGS=-Wno-deprecated-literal-operator)'
+        if old in t:
+            f.write_text(t.replace(old, new))
+            print('Patched FindPoly.cmake')
+        "
+
     - name: Build cvc5 (static)
       if: steps.cache-static.outputs.cache-hit != 'true'
       shell: bash

cvc5-sys/build.rs

@@ -252,6 +252,45 @@ fn check_cvc5_version(cvc5_dir: &Path, expected: &str) {
     println!("cargo:rerun-if-changed={}", version_file.display());
 }
 
+/// Patch `cmake/FindPoly.cmake` in the cvc5 source tree so the
+/// `-Wno-deprecated-literal-operator` flag is always passed to the
+/// Poly-EP ExternalProject, not only for WASM builds. This fixes a
+/// build failure on Apple Clang 21+ (macOS 26+) where `gmpxx.h`
+/// user-defined literal operators trigger `-Werror`.
+///
+/// The patch is idempotent: if the file was already patched (or doesn't
+/// exist), it is a no-op.
+#[cfg(feature = "static")]
+fn patch_find_poly_cmake(cvc5_dir: &Path) {
+    let cmake_file = cvc5_dir.join("cmake/FindPoly.cmake");
+    if !cmake_file.exists() {
+        return;
+    }
+    let content = fs::read_to_string(&cmake_file).expect("Failed to read FindPoly.cmake");
+
+    // The upstream file conditionally sets POLY_CXX_FLAGS only for WASM:
+    //
+    //   set(POLY_CXX_FLAGS "")
+    //   if(NOT(WASM STREQUAL "OFF"))
+    //     set(POLY_CXX_FLAGS -DCMAKE_CXX_FLAGS=-Wno-error=deprecated-literal-operator)
+    //   endif()
+    //
+    // Replace with an unconditional assignment using the strong form of
+    // the flag (-Wno- instead of -Wno-error=), which suppresses the
+    // warning entirely regardless of -Werror ordering.
+    let old = r#"set(POLY_CXX_FLAGS "")
+  if(NOT(WASM STREQUAL "OFF"))
+    set(POLY_CXX_FLAGS -DCMAKE_CXX_FLAGS=-Wno-error=deprecated-literal-operator)
+  endif()"#;
+    let new = r#"set(POLY_CXX_FLAGS -DCMAKE_CXX_FLAGS=-Wno-deprecated-literal-operator)"#;
+
+    if content.contains(old) {
+        let patched = content.replace(old, new);
+        fs::write(&cmake_file, patched).expect("Failed to write FindPoly.cmake");
+        eprintln!("Patched FindPoly.cmake: unconditional -Wno-deprecated-literal-operator");
+    }
+}
+
 // return (include path, lib path) if exist
 
 #[cfg(unix)]
@@ -283,6 +322,17 @@ fn ensure_cvc5_built_and_install() -> (Option<PathBuf>, Option<PathBuf>) {
 
     let build_dir = cvc5_dir.join("build");
 
+    // Patch FindPoly.cmake to fix the deprecated-literal-operator build
+    // failure on Apple Clang 21+ (macOS 26+). The existing cmake file
+    // uses -Wno-error=deprecated-literal-operator (the weak form), which
+    // only prevents -Werror from promoting the warning. But libpoly's
+    // CMakeLists.txt adds -Werror via target_compile_options, which
+    // appears after CMAKE_CXX_FLAGS on the command line, overriding the
+    // weak form. The strong form -Wno-deprecated-literal-operator
+    // suppresses the warning entirely, so -Werror has nothing to promote.
+    // See https://github.com/cvc5/cvc5-rs/issues/56
+    patch_find_poly_cmake(&cvc5_dir);
+
     let status = Command::new("bash")
         .arg(&configure)
         .arg("--static")