From b0fc1922c578121c195c78e1fe88f15ac22e36ec Mon Sep 17 00:00:00 2001
From: Ashish Sharma <ashish.sharma@espressif.com>
Date: Fri, 5 Jun 2026 15:01:56 +0800
Subject: [PATCH] fix(mbedtls): fixes build failure with clang21

Closes https://github.com/espressif/esp-idf/issues/18456
---
 components/mbedtls/CMakeLists.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/components/mbedtls/CMakeLists.txt b/components/mbedtls/CMakeLists.txt
index 7fb2eecbb49..9168ba84a84 100644
--- a/components/mbedtls/CMakeLists.txt
+++ b/components/mbedtls/CMakeLists.txt
@@ -155,6 +155,14 @@ endif()
 # clang produces an unreachable-code warning.
 if(CMAKE_C_COMPILER_ID MATCHES "Clang")
     target_compile_options(mbedcrypto PRIVATE "-Wno-unreachable-code")
+    # While building mbedtls/library/x509_crt.c, clang 21 produces an
+    # uninitialized-const-pointer warning. The warning flag only exists in
+    # newer clang versions, so probe for it before use.
+    include(CheckCCompilerFlag)
+    check_c_compiler_flag("-Wuninitialized-const-pointer" C_COMPILER_HAS_UNINIT_CONST_PTR_WARNING)
+    if(C_COMPILER_HAS_UNINIT_CONST_PTR_WARNING)
+        target_compile_options(mbedx509 PRIVATE "-Wno-uninitialized-const-pointer")
+    endif()
 endif()
 
 # net_sockets.c should only be compiled if BSD socket functions are available.