From 8b31fda810e7494a8eeb17ddb610797cefe29423 Mon Sep 17 00:00:00 2001
From: Hans Dembinski <HDembinski@users.noreply.github.com>
Date: Mon, 15 Apr 2024 09:52:04 +0200
Subject: [PATCH] check for odr violations and fix odr violation (#985)

Closes #976

This fixes an ODR violation and adds more warnings regarding ODR
violations to the standard build flags (which are treated as errors).
---
 CMakeLists.txt      | 14 +++++++++++++-
 src/type_caster.hpp |  7 +++----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index eb69d67f7..b057ebe0a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -85,8 +85,20 @@ set(SOURCES_B
 pybind11_add_module(_core MODULE ${SOURCES_A} ${SOURCES_B})
 if(MSVC)
   target_compile_options(_core PRIVATE /std:c++14 /Y-)
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  # lots of warnings from gcc, including odr violations
+  target_compile_options(
+    _core
+    PRIVATE -Wall
+            -Wextra
+            -pedantic
+            -Werror
+            -fstrict-aliasing
+            -Werror=odr
+            -Werror=lto-type-mismatch
+            -Werror=strict-aliasing)
 else()
-  # lots of warnings from clang and gcc
+  # lots of warnings from clang
   target_compile_options(_core PRIVATE -Wall -Wextra -pedantic -Werror
                                        -fstrict-aliasing)
 endif()
diff --git a/src/type_caster.hpp b/src/type_caster.hpp
index db8022289..9b0ae5845 100644
--- a/src/type_caster.hpp
+++ b/src/type_caster.hpp
@@ -1,4 +1,3 @@
-#include <algorithm>
 #include <pybind11/numpy.h>
 #include <pybind11/pybind11.h>
 #include <vector>
@@ -6,9 +5,9 @@
 namespace pybind11 {
 namespace detail {
 
-template <typename Value>
-struct type_caster<std::vector<Value>> {
-  using vec_t = std::vector<Value>;
+template <typename Value, typename Alloc>
+struct type_caster<std::vector<Value, Alloc>> {
+  using vec_t = std::vector<Value, Alloc>;
   using value_conv = make_caster<Value>;
   using size_conv = make_caster<std::size_t>;