r22772: - Still working on the fact that readahead() is not declared (on at least one

OS) but is available for linking.  Instead of running configure tests with
  -Werror-implicit-function-declaration in developer mode (which may lead to
  different library functions being used in developer mode than when not in
  developer mode), add tests for whether readahead is declared.  If not,
  provide a replacement declaration in lib/replace.

source/configure.in

@@ -1337,19 +1337,6 @@ AC_CHECK_LIB(exc, trace_back_stack)
 # implicit declaration warnings without failing the test (in developer mode)
 ac_no_error_on_warning_CFLAGS="${CFLAGS}"
 
-# Since --enable-developer causes warnings to be treated as errors during
-# compilation, we should avoid using features that will fail to compile.
-#
-# We don't want to enable this earlier because the built-in functions such as
-# memset fail to configure properly.
-
-if test x"$samba_cv_HAVE_Werror_implicit_function_declaration" = x"yes" -a \
-        x"$developer" = xyes; then
-  CFLAGS="${CFLAGS} -Werror-implicit-function-declaration"
-  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-  ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-fi
-
 echo -n "checking for GPFS GPL libs... "
 save_LIBS="$LIBS"
 LIBS="$LIBS -lgpfs_gpl"

source/lib/replace/README

@@ -55,6 +55,11 @@ strtoull
 socketpair
 strptime
 
+These external declarations are provided for those systems which lack the
+declaration but provide the function:
+
+readahead
+
 Types:
 bool
 socklen_t

source/lib/replace/libreplace.m4

@@ -155,6 +155,7 @@ AC_CHECK_FUNCS(pread pwrite strndup strcasestr strtok_r mkdtemp socketpair)
 AC_HAVE_DECL(setresuid, [#include <unistd.h>])
 AC_HAVE_DECL(setresgid, [#include <unistd.h>])
 AC_HAVE_DECL(errno, [#include <errno.h>])
+AC_HAVE_DECL(readahead, [#include <fcntl.h>])
 
 AC_CACHE_CHECK([for secure mkstemp],samba_cv_HAVE_SECURE_MKSTEMP,[
 AC_TRY_RUN([#include <stdlib.h>

source/lib/replace/replace.h

@@ -111,6 +111,11 @@ extern char *sys_errlist[];
 extern int errno;
 #endif
 
+#if defined(HAVE_LINUX_READAHEAD) && ! defined(HAVE_READAHEAD_DECL)
+ssize_t readahead(int fd, off64_t offset, size_t count);
+#endif
+
+
 #ifndef HAVE_STRDUP
 #define strdup rep_strdup
 char *rep_strdup(const char *s);