From 463591663c2421b3436edc446d173380d6a6e106 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Tue, 19 May 2020 08:13:13 -0700
Subject: [PATCH] Check that aligned_alloc is available with cmake

Some compilers support C++17 even on targets that lack required functions.
Projects that want to force C++17 will then run into a problem with
std::aligned_alloc not existing on those targets, so it needs to be explicitly
checked for. The alternative is to simply never use it even when it would be
available.
---
 CMakeLists.txt      | 13 ++++++++++---
 common/almalloc.cpp |  4 ++--
 config.h.in         |  3 +++
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 208a275f..64c8116e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -449,9 +449,16 @@ IF(HAVE_INTRIN_H)
         }" HAVE_BITSCANFORWARD_INTRINSIC)
 ENDIF()
 
-CHECK_SYMBOL_EXISTS(posix_memalign   stdlib.h HAVE_POSIX_MEMALIGN)
-CHECK_SYMBOL_EXISTS(_aligned_malloc  malloc.h HAVE__ALIGNED_MALLOC)
-CHECK_SYMBOL_EXISTS(proc_pidpath     libproc.h HAVE_PROC_PIDPATH)
+check_cxx_source_compiles("#include <cstdlib>
+int main()
+{
+    void *ptr{std::aligned_alloc(alignof(int), sizeof(int))};
+    std::free(ptr);
+    return 0;
+}" HAVE_STD_ALIGNED_ALLOC)
+check_symbol_exists(posix_memalign   stdlib.h HAVE_POSIX_MEMALIGN)
+check_symbol_exists(_aligned_malloc  malloc.h HAVE__ALIGNED_MALLOC)
+check_symbol_exists(proc_pidpath     libproc.h HAVE_PROC_PIDPATH)
 
 IF(NOT WIN32)
     # We need pthreads outside of Windows, for semaphores. It's also used to
diff --git a/common/almalloc.cpp b/common/almalloc.cpp
index 5b679b75..806cb4ab 100644
--- a/common/almalloc.cpp
+++ b/common/almalloc.cpp
@@ -17,7 +17,7 @@ void *al_malloc(size_t alignment, size_t size)
     assert((alignment & (alignment-1)) == 0);
     alignment = std::max(alignment, alignof(std::max_align_t));
 
-#if __cplusplus >= 201703L
+#if defined(HAVE_STD_ALIGNED_ALLOC)
     size = (size+(alignment-1))&~(alignment-1);
     return std::aligned_alloc(alignment, size);
 #elif defined(HAVE_POSIX_MEMALIGN)
@@ -48,7 +48,7 @@ void *al_calloc(size_t alignment, size_t size)
 
 void al_free(void *ptr) noexcept
 {
-#if (__cplusplus >= 201703L) || defined(HAVE_POSIX_MEMALIGN)
+#if defined(HAVE_STD_ALIGNED_ALLOC) || defined(HAVE_POSIX_MEMALIGN)
     std::free(ptr);
 #elif defined(HAVE__ALIGNED_MALLOC)
     _aligned_free(ptr);
diff --git a/config.h.in b/config.h.in
index 29a10b20..75aacc0d 100644
--- a/config.h.in
+++ b/config.h.in
@@ -8,6 +8,9 @@
 /* Define if HRTF data is embedded in the library */
 #cmakedefine ALSOFT_EMBED_HRTF_DATA
 
+/* Define if we have the std::aligned_alloc function */
+#cmakedefine HAVE_STD_ALIGNED_ALLOC
+
 /* Define if we have the posix_memalign function */
 #cmakedefine HAVE_POSIX_MEMALIGN