[PATCH] getcwd-lgpl: fix m4 to match relaxed test for BSD

[Eric Blake]

Commit c6dc8f1 changed test-getcwd-lgpl to allow BSD behavior
where getcwd(NULL,1) allocates the proper size, in addition to
the glibc behavior of allocating exactly one byte then failing
with ERANGE.  But the m4 test was still rejecting the former
behavior.

However, merely fixing the test to avoid probing the behavior
would be a regression of commit 8585ce2, since it was the only
reason why rpl_getcwd was being compiled on mingw.  Hence, we
have to add a signature check in its place to keep mingw happy.

* m4/getcwd.m4 (gl_FUNC_GETCWD_NULL): Relax probe.
(gl_FUNC_GETCWD_SIGNATURE): New macro.
(gl_FUNC_GETCWD_LGPL, gl_FUNC_GETCWD): Use it.
* doc/posix-functions/getcwd.texi (getcwd): Tweak mentions of
signature problem.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog                       |    7 +++++++
 doc/posix-functions/getcwd.texi |    3 ++-
 m4/getcwd.m4                    |   33 +++++++++++++++++++++++++--------
 3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 7c8781f..465a31f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2011-08-17  Eric Blake  <address@hidden>

+       getcwd-lgpl: fix m4 to match relaxed test for BSD
+       * m4/getcwd.m4 (gl_FUNC_GETCWD_NULL): Relax probe.
+       (gl_FUNC_GETCWD_SIGNATURE): New macro.
+       (gl_FUNC_GETCWD_LGPL, gl_FUNC_GETCWD): Use it.
+       * doc/posix-functions/getcwd.texi (getcwd): Tweak mentions of
+       signature problem.
+
        getcwd: fix compilation on mingw64
        * lib/unistd.in.h (includes) [mingw]: Include <direct.h> for
        getcwd.
diff --git a/doc/posix-functions/getcwd.texi b/doc/posix-functions/getcwd.texi
index ffb5086..8b471be 100644
--- a/doc/posix-functions/getcwd.texi
+++ b/doc/posix-functions/getcwd.texi
@@ -14,7 +14,8 @@ getcwd
 On some other platforms, this call is not allowed.
 @item
 On some platforms, the prototype for @code{getcwd} uses @code{int}
-instead of @code{size_t} for the size argument:
+instead of @code{size_t} for the size argument when using non-standard
+headers, and the declaration is missing from @code{<unistd.h>}:
 mingw.
 @item
 On some platforms, @code{getcwd (buf, 0)} fails with @code{ERANGE}
diff --git a/m4/getcwd.m4 b/m4/getcwd.m4
index 269fdd7..d3bbe59 100644
--- a/m4/getcwd.m4
+++ b/m4/getcwd.m4
@@ -6,7 +6,7 @@
 # with or without modifications, as long as this notice is preserved.

 # Written by Paul Eggert.
-# serial 7
+# serial 8

 AC_DEFUN([gl_FUNC_GETCWD_NULL],
   [
@@ -37,9 +37,6 @@ AC_DEFUN([gl_FUNC_GETCWD_NULL],
                return 0;
              }
 #endif
-         /* If size is non-zero, allocation must fail if size is too small */
-         if (getcwd (NULL, 1))
-           return 5;
          ]])],
         [gl_cv_func_getcwd_null=yes],
         [gl_cv_func_getcwd_null=no],
@@ -55,6 +52,24 @@ AC_DEFUN([gl_FUNC_GETCWD_NULL],
         ]])])
 ])

+AC_DEFUN([gl_FUNC_GETCWD_SIGNATURE],
+[
+  AC_CACHE_CHECK([for getcwd with POSIX signature],
+    [gl_cv_func_getcwd_posix_signature],
+    [AC_COMPILE_IFELSE(
+      [AC_LANG_PROGRAM(
+         [[#include <unistd.h>]],
+         [[extern
+           #ifdef __cplusplus
+           "C"
+           #endif
+           char *getcwd (char *, size_t);
+         ]])
+      ],
+      [gl_cv_func_getcwd_posix_signature=yes],
+      [gl_cv_func_getcwd_posix_signature=no])
+   ])
+])

 dnl Guarantee that getcwd will malloc with a NULL first argument.  Assumes
 dnl that either the system getcwd is robust, or that calling code is okay
@@ -67,9 +82,10 @@ AC_DEFUN([gl_FUNC_GETCWD_LGPL],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_GETCWD_NULL])
+  AC_REQUIRE([gl_FUNC_GETCWD_SIGNATURE])

-  case $gl_cv_func_getcwd_null in
-  *yes) ;;
+  case $gl_cv_func_getcwd_null,$gl_cv_func_getcwd_posix_signature in
+  *yes,yes) ;;
   *)
     dnl Minimal replacement lib/getcwd-lgpl.c.
     REPLACE_GETCWD=1
@@ -83,6 +99,7 @@ AC_DEFUN([gl_FUNC_GETCWD],
 [
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_GETCWD_NULL])
+  AC_REQUIRE([gl_FUNC_GETCWD_SIGNATURE])
   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles

   gl_abort_bug=no
@@ -94,8 +111,8 @@ AC_DEFUN([gl_FUNC_GETCWD],
     gl_FUNC_GETCWD_ABORT_BUG([gl_abort_bug=yes]);;
   esac

-  case $gl_cv_func_getcwd_null,$gl_cv_func_getcwd_path_max,$gl_abort_bug in
-  *yes,yes,no) ;;
+  case 
$gl_cv_func_getcwd_null,$gl_cv_func_getcwd_posix_signature$gl_cv_func_getcwd_path_max,$gl_abort_bug
 in
+  *yes,yes,yes,no) ;;
   *)
     dnl Full replacement lib/getcwd.c, overrides LGPL replacement.
     REPLACE_GETCWD=1;;
-- 
1.7.4.4