Re: Error: conflicting types for ‘sbrk’

[Eduardo A . Bustamante López]

On Wed, Mar 21, 2018 at 11:07:45AM -0300, Larissa Braz wrote:
> Hi,
> 
>  I found the following compilation error:
> 
> xmalloc.c:51:14: error: conflicting types for ‘sbrk’
>  extern char *sbrk();
>               ^
> In file included from xmalloc.c:29:0:
> /usr/include/unistd.h:1043:14: note: previous declaration of ‘sbrk’ was here
>  extern void *sbrk (intptr_t __delta) __THROW;
[...]
> #if defined (HAVE_SBRK) && !HAVE_DECL_SBRK
> extern char *sbrk();
> #endif

This declaration is conditional. It will only be evaluated if

  HAVE_SBRK=1
  HAVE_DECL_SBRK=0

These are set by the configure script based on what it can detect from your
system. It is strange that it detects a
working sbrk implementation, but no sbrk declaration.

* What source tree are you building? (i.e. git devel branch, git master branch,
  tarball?)
* Also, are you passing any special parameters to `configure' or `make'?
* Can you share the following blocks from your config.log and config.h after
  running the configure script?


    $ grep -i 'checking for.*sbrk' config.log -A5
    configure:10615: checking for sbrk
    configure:10615: gcc -o conftest -ggdb -O0 -Wno-parentheses 
-Wno-format-security   conftest.c  >&5
    configure:10615: $? = 0
    configure:10615: result: yes
    configure:10615: checking for fpurge
    configure:10615: gcc -o conftest -ggdb -O0 -Wno-parentheses 
-Wno-format-security   conftest.c  >&5
    --
    configure:14469: checking for working sbrk
    configure:14496: gcc -o conftest -ggdb -O0 -Wno-parentheses 
-Wno-format-security   conftest.c -ldl  >&5
    configure:14496: $? = 0
    configure:14496: ./conftest
    configure:14496: $? = 0
    configure:14506: result: yes
    
    $ grep SBRK config.h
    #define HAVE_DECL_SBRK 1
    #define HAVE_SBRK 1