[GNUnet-SVN] [gnurl] 90/208: gtls: fix build when sizeof(long) < sizeof(void *)

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ng0 pushed a commit to annotated tag gnurl-7.55.0
in repository gnurl.

commit c0cdc68c7eacaa4fda3e2324f8618b6bbe038983
Author: Johannes Schindelin <address@hidden>
AuthorDate: Mon Jun 26 23:15:22 2017 +0200

    gtls: fix build when sizeof(long) < sizeof(void *)
    
    - Change gnutls pointer/int macros to pointer/curl_socket_t.
      Prior to this change they used long type as well.
    
    The size of the `long` data type can be shorter than that of pointer
    types. This is the case most notably on Windows.
    
    If C99 were acceptable, we could simply use `intptr_t` here. But we
    want to retain C89 compatibility.
    
    Simply use the trick of performing pointer arithmetic with the NULL
    pointer: to convert an integer `i` to a pointer, simply take the
    address of the `i`th element of a hypothetical character array
    starting at address NULL. To convert back, simply cast the pointer
    difference.
    
    Thanks to Jay Satiro for the initial modification to use curl_socket_t
    instead of int/long.
    
    Closes #1617
    
    Signed-off-by: Johannes Schindelin <address@hidden>
---
 lib/vtls/gtls.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/lib/vtls/gtls.c b/lib/vtls/gtls.c
index cbbb61f76..d55f995e8 100644
--- a/lib/vtls/gtls.c
+++ b/lib/vtls/gtls.c
@@ -60,15 +60,13 @@
 /* The last #include file should be: */
 #include "memdebug.h"
 
-/*
- Some hackish cast macros based on:
- https://developer.gnome.org/glib/unstable/glib-Type-Conversion-Macros.html
-*/
-#ifndef GNUTLS_POINTER_TO_INT_CAST
-#define GNUTLS_POINTER_TO_INT_CAST(p) ((int) (long) (p))
+#ifndef GNUTLS_POINTER_TO_SOCKET_CAST
+#define GNUTLS_POINTER_TO_SOCKET_CAST(p) \
+  ((curl_socket_t) ((char *)(p) - (char *)NULL))
 #endif
-#ifndef GNUTLS_INT_TO_POINTER_CAST
-#define GNUTLS_INT_TO_POINTER_CAST(i) ((void *) (long) (i))
+#ifndef GNUTLS_SOCKET_TO_POINTER_CAST
+#define GNUTLS_SOCKET_TO_POINTER_CAST(s) \
+  ((void *) ((char *)NULL + (s)))
 #endif
 
 /* Enable GnuTLS debugging by defining GTLSDEBUG */
@@ -153,7 +151,7 @@ static int gtls_mapped_sockerrno(void)
 
 static ssize_t Curl_gtls_push(void *s, const void *buf, size_t len)
 {
-  ssize_t ret = swrite(GNUTLS_POINTER_TO_INT_CAST(s), buf, len);
+  ssize_t ret = swrite(GNUTLS_POINTER_TO_SOCKET_CAST(s), buf, len);
 #if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
   if(ret < 0)
     gnutls_transport_set_global_errno(gtls_mapped_sockerrno());
@@ -163,7 +161,7 @@ static ssize_t Curl_gtls_push(void *s, const void *buf, 
size_t len)
 
 static ssize_t Curl_gtls_pull(void *s, void *buf, size_t len)
 {
-  ssize_t ret = sread(GNUTLS_POINTER_TO_INT_CAST(s), buf, len);
+  ssize_t ret = sread(GNUTLS_POINTER_TO_SOCKET_CAST(s), buf, len);
 #if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
   if(ret < 0)
     gnutls_transport_set_global_errno(gtls_mapped_sockerrno());
@@ -850,7 +848,7 @@ gtls_connect_step1(struct connectdata *conn,
   }
   else {
     /* file descriptor for the socket */
-    transport_ptr = GNUTLS_INT_TO_POINTER_CAST(conn->sock[sockindex]);
+    transport_ptr = GNUTLS_SOCKET_TO_POINTER_CAST(conn->sock[sockindex]);
     gnutls_transport_push = Curl_gtls_push;
     gnutls_transport_pull = Curl_gtls_pull;
   }

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