From 6d1d5ccb1c66446f2f25c02c06aaf559be9ee8d5 Mon Sep 17 00:00:00 2001
From: Alexey Lapshin <alexey.lapshin@espressif.com>
Date: Thu, 21 Nov 2024 17:37:16 +0700
Subject: [PATCH 1/2] feat(build): add CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR
 choise option

Allow to disable implicit inlining of constexpr functions from libstdc++.
This is a known GCC issue https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93008
that may affect C++ application size depending on its structure.
---
 CMakeLists.txt                          |  8 +++++++
 Kconfig                                 | 28 +++++++++++++++++++++++++
 docs/en/api-guides/performance/size.rst |  5 +++++
 3 files changed, 41 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d21d2a38ec..be10166d5d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -175,6 +175,14 @@ if(CMAKE_C_COMPILER_ID MATCHES "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_GREATE
     list(APPEND c_compile_options "-fzero-init-padding-bits=all" "-fno-malloc-dce")
 endif()
 
+if(CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD_CONSTEXPR)
+    list(APPEND cxx_compile_options "-D_GLIBCXX20_CONSTEXPR=__attribute__((cold)) constexpr")
+    list(APPEND cxx_compile_options "-D_GLIBCXX23_CONSTEXPR=__attribute__((cold)) constexpr")
+elseif(CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD)
+    list(APPEND cxx_compile_options "-D_GLIBCXX20_CONSTEXPR=__attribute__((cold))")
+    list(APPEND cxx_compile_options "-D_GLIBCXX23_CONSTEXPR=__attribute__((cold))")
+endif()
+
 __generate_prefix_map(prefix_map_compile_options)
 list(APPEND compile_options ${prefix_map_compile_options})
 
diff --git a/Kconfig b/Kconfig
index 5e19164a5e..a7739d04af 100644
--- a/Kconfig
+++ b/Kconfig
@@ -685,6 +685,34 @@ mainmenu "Espressif IoT Development Framework Configuration"
             help
                 Enable compiler static analyzer. This may produce false-positive results and increases compile time.
 
+        choice COMPILER_CXX_GLIBCXX_CONSTEXPR
+            prompt "Define _GLIBCXX_CONSTEXPR"
+            default COMPILER_CXX_GLIBCXX_CONSTEXPR_NO_CHANGE
+            depends on IDF_TOOLCHAIN_GCC && !IDF_TARGET_LINUX
+            help
+                Modify libstdc++ _GLIBCXX20_CONSTEXPR and _GLIBCXX23_CONSTEXPR definitions to provide size
+                optimizations. The total size optimization depends on the application's structure.
+                There is no robust way to determine which option would be better in a particular case.
+                Please try all available options to find the best size optimization.
+
+            config COMPILER_CXX_GLIBCXX_CONSTEXPR_NO_CHANGE
+                bool "No change"
+                help
+                    Use default _GLIBCXX20_CONSTEXPR and _GLIBCXX23_CONSTEXPR defined in libstdc++
+
+            config COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD_CONSTEXPR
+                bool "_GLIBCXX2X_CONSTEXPR=__attribute__((cold)) constexpr"
+                help
+                    Define _GLIBCXX20_CONSTEXPR=__attribute__((cold)) constexpr
+                    Define _GLIBCXX23_CONSTEXPR=__attribute__((cold)) constexpr
+
+            config COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD
+                bool "_GLIBCXX2X_CONSTEXPR=__attribute__((cold))"
+                help
+                    Define _GLIBCXX20_CONSTEXPR=__attribute__((cold)).
+                    Define _GLIBCXX23_CONSTEXPR=__attribute__((cold)).
+        endchoice
+
     endmenu # Compiler Options
 
     menu "Component config"
diff --git a/docs/en/api-guides/performance/size.rst b/docs/en/api-guides/performance/size.rst
index 45e4004bc4..7cd74d538b 100644
--- a/docs/en/api-guides/performance/size.rst
+++ b/docs/en/api-guides/performance/size.rst
@@ -194,6 +194,11 @@ Enabling "Nano" formatting reduces the stack usage of each function that calls `
 
 .. _Newlib README file: https://sourceware.org/newlib/README
 
+libstdc++
+@@@@@@@@@
+
+- Enable :ref:`CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD_CONSTEXPR<CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD_CONSTEXPR>` or :ref:`CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD<CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD>` to observe the impact on your application's binary size.
+
 .. _minimizing_binary_mbedtls:
 
 MbedTLS Features

From f53f02f3b52f5121728a819eb4317735726dc5b5 Mon Sep 17 00:00:00 2001
From: renpeiying <renpeiying@espressif.com>
Date: Sun, 27 Apr 2025 15:35:04 +0800
Subject: [PATCH 2/2] docs(size): update CN translation for size.rst

---
 docs/zh_CN/api-guides/performance/size.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/docs/zh_CN/api-guides/performance/size.rst b/docs/zh_CN/api-guides/performance/size.rst
index f7696d0792..056663b516 100644
--- a/docs/zh_CN/api-guides/performance/size.rst
+++ b/docs/zh_CN/api-guides/performance/size.rst
@@ -194,6 +194,11 @@ ESP-IDF 的 I/O 函数（ ``printf()`` 和 ``scanf()`` 等）默认使用 Newlib
 
 .. _Newlib README 文件: https://sourceware.org/newlib/README
 
+libstdc++
+@@@@@@@@@
+
+- 启用 :ref:`CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD_CONSTEXPR<CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD_CONSTEXPR>` 或 :ref:`CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD<CONFIG_COMPILER_CXX_GLIBCXX_CONSTEXPR_COLD>` 观察对应用程序二进制大小的影响。
+
 .. _minimizing_binary_mbedtls:
 
 MbedTLS 功能