2006-05-26 Paul Eggert <eggert@cs.ucla.edu>
+ * doc/autoconf.texi (Particular Programs, Limitations of Usual Tools):
+ Use better wording to talk about AC_PROG_MKDIR_P's thread-safety.
+ Don't use the term "thread-safe" to talk about mkdir race
+ conditions, since the problem is more a process than a thread
+ issue. Problem reported by Stepan Kasal in:
+ http://lists.gnu.org/archive/html/autoconf-patches/2006-05/msg00088.html
+ * lib/autoconf/programs.m4 (AC_PROG_MKDIR_P): Use code that mimics
+ the test for 'install' more closely. Look at MKDIR_P first.
+ Look in the PATH, and at /opt/sfw/bin.
+ Look for a 'gmkdir' program as well (Solaris 10 /opt/sfw/bin/gmkdir).
+ Don't bother to try mkdir -p, since we already check mkdir --version;
+ just look at the version number. (There's no easy way to check
+ for race-free implementations.)
+ * tests/tools.at (autoconf: subdirectories): Adjust to above
+ changes, since MKDIR_P now might end in "/mkdir -p".
+
* doc/autoconf.texi (autoheader Invocation): Mention that the
first arg of AC_DEFINE_UNQUOTED must not be a literal.
Problem reported by Ben Pfaff in
@ovindex MKDIR_P
Set output variable @code{MKDIR_P} to a program that ensures that for
each argument, a directory named by this argument exists, creating it
-and its parent directories if needed. The program is checked to make
-sure that it is thread-safe (@pxref{Limitations of Usual Tools}).
+and its parent directories if needed, and without race conditions when
+two instances of the program attempt to make the same directory at
+nearly the same time.
This macro uses the @samp{mkdir -p} command if possible. Otherwise, it
falls back on invoking @command{install-sh} with the @option{-d} option,
so your package should
contain @file{install-sh} as described under @code{AC_PROG_INSTALL}.
A @file{install-sh} file that predates Autoconf 2.60 or Automake 1.10
-won't be thread-safe, so if you want to support parallel installs from
+is vulnerable to race conditions, so if you want to support parallel
+installs from
different packages into the same directory you need to make sure you
have an up-to-date @file{install-sh}. In particular, be careful about
using @samp{autoreconf -if} if your Automake predates Automake 1.10.
in M4sh}), but it sets an output variable intended for use in other
files, whereas @code{AS_MKDIR_P} is intended for use in scripts like
@command{configure}. Also, @code{AS_MKDIR_P} does not accept options,
-but if you are willing to assume Posix 1003.2-1992 or later, a
-@code{MKDIR_P} can use the @option{-m} option, e.g., a makefile might
+but @code{MKDIR_P} can use the @option{-m} option, e.g., a makefile might
invoke @code{$(MKDIR_P) -m 0 dir} to create an inaccessible directory.
+Finally, @code{AS_MKDIR_P} does not check for race condition
+vulnerability, whereas @code{AC_PROG_MKDIR_P} does.
@end defmac
@defmac AC_PROG_LEX
directory. The @acronym{GNU} Core Utilities 5.1.0 @command{mkdir}
succeeds, but Solaris @command{mkdir} fails.
-Not all @code{mkdir -p} implementations are thread-safe. When it is not
-and you call @code{mkdir -p a/b} and @code{mkdir -p a/c} at the same
-time, both will detect that @file{a/} is missing, one will create
-@file{a/}, then the other will try to create @file{a/} and die with a
-@code{File exists} error. At least Solaris 10, Net@acronym{BSD} 1.6, and Open@acronym{BSD}
-3.4 have an unsafe @code{mkdir -p}. The @acronym{GNU} Core Utilities
+Traditional @code{mkdir -p} implementations suffer from race conditions.
+For example, if you invoke @code{mkdir -p a/b} and @code{mkdir -p a/c}
+at the same time, both processes might detect that @file{a} is missing,
+one might create @file{a}, then the other might try to create @file{a}
+and fail with a @code{File exists} diagnostic. At least Solaris 10,
+Net@acronym{BSD} 1.6, and Open@acronym{BSD} 3.4 are vulnerable to race
+conditions. The @acronym{GNU} Core Utilities
(since @samp{fileutils}
-version 4.0c), Free@acronym{BSD} 5.0, and Net@acronym{BSD}-current are
+version 4.1), Free@acronym{BSD} 5.0, and Net@acronym{BSD}-current are
known to have a
race-free @code{mkdir -p}. This possible race is harmful in parallel
builds when several @file{Makefile} rules call @code{mkdir -p} to
construct directories. You may use
@code{install-sh -d} as a safe replacement, provided this script is
recent enough; the copy shipped with Autoconf 2.60 and Automake 1.10 is
-OK, but copies from older versions are not thread-safe either.
+OK, but copies from older versions are vulnerable.
@item @command{mktemp}
# concurrently, both version can detect that a/ is missing, but only
# one can create it and the other will error out. Consequently we
# restrict ourselves to GNU mkdir (using the --version option ensures
-# this.)
+# this).
#
# Automake used to define mkdir_p as `mkdir -p .', in order to
# allow $(mkdir_p) to be used without argument. As in
[AC_REQUIRE([AC_CONFIG_AUX_DIR_DEFAULT])dnl
AC_REQUIRE_AUX_FILE([install-sh])dnl
AC_MSG_CHECKING([for a thread-safe mkdir -p])
-if mkdir -p --version . >/dev/null 2>&1 && test ! -d ./--version; then
- MKDIR_P='mkdir -p'
-else
- for ac_d in ./-p ./--version
- do
- test -d $ac_d && rmdir $ac_d
- done
- MKDIR_P="$ac_install_sh -d"
+if test -z "$MKDIR_P"; then
+ AC_CACHE_VAL([ac_cv_path_mkdir],
+ [_AS_PATH_WALK([$PATH$PATH_SEPARATOR/opt/sfw/bin],
+ [for ac_prog in mkdir gmkdir; do
+ for ac_exec_ext in '' $ac_executable_extensions; do
+ AS_EXECUTABLE_P(["$as_dir/$ac_prog$ac_exec_ext"]) || continue
+ case `"$as_dir/$ac_prog$ac_exec_ext" --version 2>&1` in #(
+ 'mkdir (GNU coreutils) '* | \
+ 'mkdir (coreutils) '* | \
+ 'mkdir (fileutils) '4.1*)
+ ac_cv_path_mkdir=$as_dir/$ac_prog$ac_exec_ext
+ break 3;;
+ esac
+ done
+ done])])
+ if test "${ac_cv_path_mkdir+set}" = set; then
+ MKDIR_P="$ac_cv_path_mkdir -p"
+ else
+ # As a last resort, use the slow shell script. Don't cache a
+ # value for MKDIR_P within a source directory, because that will
+ # break other packages using the cache if that directory is
+ # removed, or if the value is a relative name.
+ test -d ./--version && rmdir ./--version
+ MKDIR_P="$ac_install_sh -d"
+ fi
fi
dnl Do special magic for MKDIR_P instead of AC_SUBST, to get
dnl relative names right.
projects / thirdparty / autoconf.git / commitdiff
