From 5329f80b32f965bd528496bb30916e7b268473c2 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Sun, 5 Mar 2023 17:51:55 +0100
Subject: [PATCH] Fix build errors with Cygwin (fixes #3639)

---
 src/filemanager.cpp      |  5 +++--
 src/proj_internal.h      | 25 +++++++++++++++++++++----
 test/unit/CMakeLists.txt |  8 ++++++++
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/filemanager.cpp b/src/filemanager.cpp
index 67215e1428..69a1cf6a94 100644
--- a/src/filemanager.cpp
+++ b/src/filemanager.cpp
@@ -29,6 +29,9 @@
 #define FROM_PROJ_CPP
 #endif
 
+// proj_config.h must be included before testing HAVE_LIBDL
+#include "proj_config.h"
+
 #if defined(HAVE_LIBDL) && !defined(_GNU_SOURCE)
 // Required for dladdr() on Cygwin
 #define _GNU_SOURCE
@@ -50,8 +53,6 @@
 
 #include <sys/stat.h>
 
-#include "proj_config.h"
-
 #ifdef _WIN32
 #if defined(WINAPI_FAMILY) && (WINAPI_FAMILY == WINAPI_FAMILY_APP)
 #define UWP 1
diff --git a/src/proj_internal.h b/src/proj_internal.h
index 785c849235..c50f1a6166 100644
--- a/src/proj_internal.h
+++ b/src/proj_internal.h
@@ -132,8 +132,21 @@
  */
 #ifndef M_PI
 #define M_PI 3.14159265358979323846
+#endif
+
+#ifndef M_1_PI
+#define M_1_PI 0.318309886183790671538
+#endif
+
+#ifndef M_PI_2
 #define M_PI_2 1.57079632679489661923
+#endif
+
+#ifndef M_PI_4
 #define M_PI_4 0.78539816339744830962
+#endif
+
+#ifndef M_2_PI
 #define M_2_PI 0.63661977236758134308
 #endif
 
@@ -143,10 +156,14 @@
 #endif
 
 /* some more useful math constants and aliases */
-#define M_FORTPI M_PI_4                       /* pi/4 */
-#define M_HALFPI M_PI_2                       /* pi/2 */
-#define M_PI_HALFPI 4.71238898038468985769    /* 1.5*pi */
-#define M_TWOPI 6.28318530717958647693        /* 2*pi */
+#define M_FORTPI M_PI_4                    /* pi/4 */
+#define M_HALFPI M_PI_2                    /* pi/2 */
+#define M_PI_HALFPI 4.71238898038468985769 /* 1.5*pi */
+
+#ifndef M_TWOPI
+#define M_TWOPI 6.28318530717958647693 /* 2*pi */
+#endif
+
 #define M_TWO_D_PI M_2_PI                     /* 2/pi */
 #define M_TWOPI_HALFPI 7.85398163397448309616 /* 2.5*pi */
 
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index e1221ef4eb..1ec1dcb892 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -35,6 +35,14 @@ message(STATUS "Using internal GTest")
 configure_file(
   ${PROJ_SOURCE_DIR}/test/googletest/CMakeLists.txt.in
   ${PROJ_BINARY_DIR}/googletest-download/CMakeLists.txt)
+
+if(CYGWIN)
+# needed at least with gcc 11.3.0 Cygwin, otherwise build errors in
+# in googletest-src/googletest/include/gtest/internal/gtest-port.h related to
+# fileno() and other functions, when building gtest or including it
+add_definitions(-D_GNU_SOURCE)
+endif()
+
 execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
   RESULT_VARIABLE result
   WORKING_DIRECTORY ${PROJ_BINARY_DIR}/googletest-download)