getcwd-lgpl: relax test for FreeBSD

getcwd(NULL, 1) mallocs a larger buffer on BSD, rather than failing
with ERANGE as on glibc.  This behavior difference is not worth
coding around, as it is an uncommon use of getcwd in the first place.

* doc/posix-functions/getcwd.texi (getcwd): Document portability
issue.
* tests/test-getcwd-lgpl.c (main): Relax test.
Reported by Matthias Bolte.

Signed-off-by: Eric Blake <eblake@redhat.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/doc/posix-functions/getcwd.texi b/doc/posix-functions/getcwd.texi
index 1f6dd187d2..a49a8990dc 100644
--- a/doc/posix-functions/getcwd.texi
+++ b/doc/posix-functions/getcwd.texi
@@ -11,8 +11,7 @@ Portability problems fixed by either Gnulib module @code{getcwd} or
 @itemize
 @item
 On glibc platforms, @code{getcwd (NULL, n)} allocates memory for the result.
-On some other platforms, this call is not allowed.  Conversely, mingw fails
-to honor non-zero @code{n}.
+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:
@@ -30,4 +29,11 @@ correctly on some platforms.
 
 Portability problems not fixed by Gnulib:
 @itemize
+@item
+When using @code{getcwd(NULL, nonzero)}, some platforms, such as glibc
+or cygwin, allocate exactly @code{nonzero} bytes and fail with
+@code{ERANGE} if it was not big enough, while other platforms, such as
+FreeBSD or mingw, ignore the size argument and allocate whatever size
+is necessary.  If this call succeeds, an application cannot portably
+access beyond the string length of the result.
 @end itemize