[lwip-devel] [bug #47625] Error in compilation of C++ source using netifapi macros

[Freddie Chopin]

URL:
  <http://savannah.nongnu.org/bugs/?47625>

                 Summary: Error in compilation of C++ source using netifapi
macros
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: freddie_chopin
            Submitted on: Tue 05 Apr 2016 08:55:56 GMT
                Category: None
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: git head

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Details:

If you try to call any macro which uses netifapi_netif_common(), so for
example netifapi_netif_set_default(), in some cases the compilation will fail
in if the source file is in C++ doesn't include "NULL" definition (from
<cstddef>). For example in this trivial case:

--- >8 --- >8 --- >8 --- >8 --- >8 --- >8 ---

#include "lwip/netifapi.h"

void f(void)
{
        struct netif netif;
        netifapi_netif_set_default(&netif);
}

--- >8 --- >8 --- >8 --- >8 --- >8 --- >8 ---

Compilation fails with error message like this:

--- >8 --- >8 --- >8 --- >8 --- >8 --- >8 ---

arm-none-eabi-g++ -Wall -Wextra -Wshadow -std=gnu++11 -g -ggdb3
-mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16 -O2
-ffunction-sections -fdata-sections -fno-rtti -fno-exceptions -MD -MP 
-IlwIP-integration/include -Iexternal/lwIP/src/include -Ioutput/include
-Iexternal/distortos/include -Wno-shadow -c test.cpp -o output/./test.o
In file included from test.cpp:1:0:
test.cpp: In function 'void f()':
external/lwIP/src/include/lwip/netifapi.h:93:87: error: invalid conversion
from 'void*' to 'netifapi_errt_fn {aka signed char (*)(netif*)}'
[-fpermissive]
 #define netifapi_netif_set_default(n) netifapi_netif_common(n,
netif_set_default, NULL)
                                                                              
        ^
test.cpp:6:2: note: in expansion of macro 'netifapi_netif_set_default'
  netifapi_netif_set_default(&netif);
  ^
external/distortos/Makefile:238: recipe for target 'output/./test.o' failed
external/lwIP/src/include/lwip/netifapi.h:87:7: note:   initializing argument
3 of 'err_t netifapi_netif_common(netif*, netifapi_void_fn,
netifapi_errt_fn)'
 err_t netifapi_netif_common(struct netif *netif, netifapi_void_fn voidfunc,
       ^
make: *** [output/./test.o] Error 1

--- >8 --- >8 --- >8 --- >8 --- >8 --- >8 ---

Including <cstddef> in the source file helps, as well as including <stddef.h>
in netifapi.h, so I think that lwIP should include this system header in all
headers where NULL is used.




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