configure: added --disable-get-easy-options

To allow disabling of the curl_easy_option APIs in a build.

Closes #5365

configure.ac

@@ -4830,6 +4830,24 @@ AC_HELP_STRING([--disable-dnsshuffle],[Disable DNS shuffling]),
        AC_MSG_RESULT(yes)
 )
 
+dnl ************************************************************
+dnl disable the curl_easy_options API
+dnl
+AC_MSG_CHECKING([whether to support curl_easy_option*])
+AC_ARG_ENABLE(get-easy-option,
+AC_HELP_STRING([--enable-get-easy-options],[Enable curl_easy_options])
+AC_HELP_STRING([--disable-get-easy-options],[Disable curl_easy_options]),
+[ case "$enableval" in
+  no)
+       AC_MSG_RESULT(no)
+       AC_DEFINE(CURL_DISABLE_GETOPTIONS, 1, [to disable curl_easy_options])
+       ;;
+  *)   AC_MSG_RESULT(yes)
+       ;;
+  esac ],
+       AC_MSG_RESULT(yes)
+)
+
 dnl ************************************************************
 dnl switch on/off alt-svc
 dnl

docs/CURL-DISABLE.md

@@ -24,6 +24,11 @@ Disable the FILE protocol
 
 Disable the FTP (and FTPS) protocol
 
+## CURL_DISABLE_GETOPTIONS
+
+Disable the `curl_easy_options` API calls that lets users get information
+about existing options to `curl_easy_setopt`.
+
 ## CURL_DISABLE_GOPHER
 
 Disable the GOPHER protocol.

lib/easygetopt.c

@@ -24,6 +24,8 @@
 #include "strcase.h"
 #include "easyoptions.h"
 
+#ifndef CURL_DISABLE_GETOPTIONS
+
 /* Lookups easy options at runtime */
 static struct curl_easyoption *lookup(const char *name, CURLoption id)
 {
@@ -71,3 +73,23 @@ curl_easy_option_next(const struct curl_easyoption *prev)
   return NULL;
 }
 
+#else
+const struct curl_easyoption *curl_easy_option_by_name(const char *name)
+{
+  (void)name;
+  return NULL;
+}
+
+const struct curl_easyoption *curl_easy_option_by_id (CURLoption id)
+{
+  (void)id;
+  return NULL;
+}
+
+const struct curl_easyoption *
+curl_easy_option_next(const struct curl_easyoption *prev)
+{
+  (void)prev;
+  return NULL;
+}
+#endif