[lwip-devel] [bug #54850] lwip definition of htonX and ntohX do not properly cast to unsigned when byte order is Big Endian

[Ivan Warren]

URL:
  <https://savannah.nongnu.org/bugs/?54850>

                 Summary: lwip definition of htonX and ntohX do not properly
cast to unsigned when byte order is Big Endian
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: ivanw
            Submitted on: Wed 17 Oct 2018 07:57:18 AM UTC
                Category: Platform ports
                Severity: 3 - Normal
              Item Group: Compiler Warning
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.1.0

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Details:

in src/include/lwip/def.h the definitions for
- lwip_ntohl
- lwip_htonl
- lwip_ntohs
- lwip_htons

on big endian systems are defined as : #define lwip_xxx(x) (x)

However, this leads to compiler warning/errors sign compares if 'x' is signed
since the result is expected to be an unsigned value (even if x is a signed
scalar).

Fixed with the following patch :

diff --git a/src/include/lwip/def.h b/src/include/lwip/def.h
index 3d6e107e..200af1c3 100644
--- a/src/include/lwip/def.h
+++ b/src/include/lwip/def.h
@@ -83,14 +83,14 @@ extern "C" {
 #endif

 #if BYTE_ORDER == BIG_ENDIAN
-#define lwip_htons(x) (x)
-#define lwip_ntohs(x) (x)
-#define lwip_htonl(x) (x)
-#define lwip_ntohl(x) (x)
-#define PP_HTONS(x) (x)
-#define PP_NTOHS(x) (x)
-#define PP_HTONL(x) (x)
-#define PP_NTOHL(x) (x)
+#define lwip_htons(x) (u16_t)(x)
+#define lwip_ntohs(x) (u16_t)(x)
+#define lwip_htonl(x) (u32_t)(x)
+#define lwip_ntohl(x) (u32_t)(x)
+#define PP_HTONS(x) (u16_t)(x)
+#define PP_NTOHS(x) (u16_t)(x)
+#define PP_HTONL(x) (u32_t)(x)
+#define PP_NTOHL(x) (u32_t)(x)
 #else /* BYTE_ORDER != BIG_ENDIAN */
 #ifndef lwip_htons
 u16_t lwip_htons(u16_t x);





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