From 19b13ea34a35fd9441316b77489effa0d4ebe269 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=BCtzel?= <markus.muetzel@gmx.de>
Date: Tue, 4 Jul 2023 17:00:59 +0200
Subject: [PATCH] CXSparse: Avoid including C header in C++ code

According to [1]: "Source files that are not intended to also be valid
ISO C should not use any of the C headers."

It is still correct to define `cs_complex_t` as `double _Complex` in C
and C++ code. But the C standard header `complex.h` shouldn't be included
in a header that can be used in C++ code. That is not a requirement. But
it is a recommendation.

Additionally, avoid inclusion of headers inside an `extern "C"` block.

[1]: https://en.cppreference.com/w/cpp/standard_library
---
 CXSparse/Config/cs.h.in | 16 ++++++++++------
 CXSparse/Include/cs.h   | 16 ++++++++++------
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/CXSparse/Config/cs.h.in b/CXSparse/Config/cs.h.in
index e73488a3d..6280e7467 100644
--- a/CXSparse/Config/cs.h.in
+++ b/CXSparse/Config/cs.h.in
@@ -27,12 +27,12 @@
 #define _CXS_H
 
 #if @CXSPARSE_USE_COMPLEX@
-#include <complex.h>
-#define cs_complex_t double _Complex
-#endif
-
-#ifdef __cplusplus
-extern "C" {
+#  ifdef __cplusplus
+#    include <complex>
+#  else
+#    include <complex.h>
+#  endif
+#  define cs_complex_t double _Complex
 #endif
 
 #define CS_VER @CXSPARSE_VERSION_MAJOR@  /* CXSparse Version */
@@ -47,6 +47,10 @@ extern "C" {
 #define cs_long_t_id    "%" PRId64
 #define cs_long_t_max   INT64_MAX
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* -------------------------------------------------------------------------- */
 /* double/int32_t version of CXSparse */
 /* -------------------------------------------------------------------------- */
diff --git a/CXSparse/Include/cs.h b/CXSparse/Include/cs.h
index 5a083f82c..e1cf17f04 100644
--- a/CXSparse/Include/cs.h
+++ b/CXSparse/Include/cs.h
@@ -27,12 +27,12 @@
 #define _CXS_H
 
 #if 1
-#include <complex.h>
-#define cs_complex_t double _Complex
-#endif
-
-#ifdef __cplusplus
-extern "C" {
+#  ifdef __cplusplus
+#    include <complex>
+#  else
+#    include <complex.h>
+#  endif
+#  define cs_complex_t double _Complex
 #endif
 
 #define CS_VER 4  /* CXSparse Version */
@@ -47,6 +47,10 @@ extern "C" {
 #define cs_long_t_id    "%" PRId64
 #define cs_long_t_max   INT64_MAX
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* -------------------------------------------------------------------------- */
 /* double/int32_t version of CXSparse */
 /* -------------------------------------------------------------------------- */