curl_setup: Ensure no more than one IDN lib is enabled

Prior to this change it was possible for libcurl to be built with both
Windows' native IDN lib (normaliz) and libidn2 enabled. It appears that
doesn't offer any benefit --and could cause a bug-- since libcurl's IDN
handling is written to use either one but not both.

Bug: https://github.com/curl/curl/issues/1441#issuecomment-297689856
Reported-by: Gisle Vanem

diff --git a/lib/curl_setup.h b/lib/curl_setup.h
index dda1c751e39756d696b5693f4d4c6626a556ad72..d22997cc999906387c74ddd183e67c45ad820b25 100644 (file)
--- a/lib/curl_setup.h
+++ b/lib/curl_setup.h
@@ -588,11 +588,15 @@ int netware_init(void);
 #endif
 #endif
 
-#if defined(HAVE_LIBIDN2) && defined(HAVE_IDN2_H)
+#if defined(HAVE_LIBIDN2) && defined(HAVE_IDN2_H) && !defined(USE_WIN32_IDN)
 /* The lib and header are present */
 #define USE_LIBIDN2
 #endif
 
+#if defined(USE_LIBIDN2) && defined(USE_WIN32_IDN)
+#error "Both libidn2 and WinIDN are enabled, choose one."
+#endif
+
 #ifndef SIZEOF_TIME_T
 /* assume default size of time_t to be 32 bit */
 #define SIZEOF_TIME_T 4