gdb: Add comment explaining autoconf variables

[termux-packages] / packages / c-ares / ares_init.c.patch

diff -u -r ../c-ares-1.10.0/ares_init.c ./ares_init.c
--- ../c-ares-1.10.0/ares_init.c	2013-02-17 11:44:02.000000000 -0500
+++ ./ares_init.c	2016-01-03 08:28:33.855590585 -0500
@@ -43,7 +43,36 @@
 #endif
 
 #if defined(ANDROID) || defined(__ANDROID__)
-#include <sys/system_properties.h>
+
+# ifdef __LP64__
+# include <dlfcn.h>
+// http://stackoverflow.com/questions/28413530/api-to-get-android-system-properties-is-removed-in-arm64-platforms
+// Android 64-bit makes __system_property_get a non-global symbol.
+// Here we provide a stub which loads the symbol from libc via dlsym.
+#define PROP_NAME_MAX 31
+#define PROP_VALUE_MAX 91
+typedef int (*PFN_SYSTEM_PROP_GET)(const char *, char *);
+int __system_property_get(const char* name, char* value)
+{
+       static PFN_SYSTEM_PROP_GET __real_system_property_get = NULL;
+       if (!__real_system_property_get) {
+               // libc.so should already be open, get a handle to it.
+               void *handle = dlopen("libc.so", RTLD_NOLOAD);
+               if (!handle) {
+                       printf("Cannot dlopen libc.so: %s.\n", dlerror());
+               } else {
+                       __real_system_property_get = (PFN_SYSTEM_PROP_GET)dlsym(handle, "__system_property_get");
+               }
+               if (!__real_system_property_get) {
+                       printf("Cannot resolve __system_property_get(): %s.\n", dlerror());
+               }
+       }
+       return (*__real_system_property_get)(name, value);
+} 
+# else
+#  include <sys/system_properties.h>
+#endif
+
 /* From the Bionic sources */
 #define DNS_PROP_NAME_PREFIX  "net.dns"
 #define MAX_DNS_PROPERTIES    8