swap32 is already defined
Index: src/external/LibRaw/src/decoders/fp_dng.cpp
--- src/external/LibRaw/src/decoders/fp_dng.cpp.orig
+++ src/external/LibRaw/src/decoders/fp_dng.cpp
@@ -572,7 +572,7 @@ _forceinline
 #else
 inline
 #endif
-void swap32(uchar *data, int len)
+void oswap32(uchar *data, int len)
 {
     unsigned *d = (unsigned*)data;
     for (int i = 0; i < len / 4; i++)
@@ -648,7 +648,7 @@ void LibRaw::uncompressed_fp_dng_load_raw()
                 else if (bytesps == 3 && (libraw_internal_data.unpacker_data.order == 0x4949)) // II-16bit
                     swap24(dst, fullrowbytes);
                 if (bytesps == 4 && difford)
-                    swap32(dst, fullrowbytes);
+                    oswap32(dst, fullrowbytes);
 
                 float lmax = expandFloats(
                     dst,
