From ad41c98cbbdb535413feae41f17893ae3f3ac051 Mon Sep 17 00:00:00 2001
From: David Callu <callu.david@gmail.com>
Date: Thu, 28 Nov 2019 12:15:20 +0100
Subject: FindPNG: add 'm' dependencies to static lib on Linux

---
 Modules/FindPNG.cmake | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Modules/FindPNG.cmake b/Modules/FindPNG.cmake
index bd400c7..f1fe89a 100644
--- a/Modules/FindPNG.cmake
+++ b/Modules/FindPNG.cmake
@@ -94,6 +94,10 @@ if(ZLIB_FOUND)
       set(PNG_INCLUDE_DIRS ${PNG_PNG_INCLUDE_DIR} ${ZLIB_INCLUDE_DIR} )
       set(PNG_INCLUDE_DIR ${PNG_INCLUDE_DIRS} ) # for backward compatibility
       set(PNG_LIBRARIES ${PNG_LIBRARY} ${ZLIB_LIBRARY})
+      if((CMAKE_SYSTEM_NAME STREQUAL "Linux") AND
+         ("${PNG_LIBRARY}" MATCHES "\\${CMAKE_STATIC_LIBRARY_SUFFIX}$"))
+        list(APPEND PNG_LIBRARIES m)
+      endif()
 
       if (CYGWIN)
         if(BUILD_SHARED_LIBS)
@@ -110,6 +114,12 @@ if(ZLIB_FOUND)
           INTERFACE_COMPILE_DEFINITIONS "${_PNG_COMPILE_DEFINITIONS}"
           INTERFACE_INCLUDE_DIRECTORIES "${PNG_INCLUDE_DIRS}"
           INTERFACE_LINK_LIBRARIES ZLIB::ZLIB)
+        if((CMAKE_SYSTEM_NAME STREQUAL "Linux") AND
+           ("${PNG_LIBRARY}" MATCHES "\\${CMAKE_STATIC_LIBRARY_SUFFIX}$"))
+          set_property(TARGET PNG::PNG APPEND PROPERTY
+            INTERFACE_LINK_LIBRARIES m)
+        endif()
+
         if(EXISTS "${PNG_LIBRARY}")
           set_target_properties(PNG::PNG PROPERTIES
             IMPORTED_LINK_INTERFACE_LANGUAGES "C"
-- 
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