Prefer PATH_MAX to MAXPATHLEN

PATH_MAX is standardized, MAXPATHLEN is not.
Also, the Gnulib pathmax module fixes some rare bugs with PATH_MAX.
So prefer PATH_MAX to MAXPATHLEN unless we know the latter is
also correct (for some platform-specific code).
* admin/merge-gnulib (GNULIB_MODULES): Add pathmax.
This module was already present, as a dependency of canonicalize-lgpl,
but now Emacs is using it directly.  Sort.
* lib-src/emacsclient.c: Include stdint.h, pathmax.h.
(get_current_dir_name): Sync to current src/sysdep.c.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/sysdep.c: Include pathmax.h.
(get_current_dir_name_or_unreachable):
Use PATH_MAX instead of MAXPATHLEN.

admin/merge-gnulib

@@ -27,9 +27,9 @@ GNULIB_URL=git://git.savannah.gnu.org/gnulib.git
 
 GNULIB_MODULES='
   alloca-opt binary-io byteswap c-ctype c-strcase
+  canonicalize-lgpl
   careadlinkat close-stream copy-file-range
   count-leading-zeros count-one-bits count-trailing-zeros
-  canonicalize-lgpl
   crypto/md5-buffer crypto/sha1-buffer crypto/sha256-buffer crypto/sha512-buffer
   d-type diffseq dosname dtoastr dtotimespec dup2
   environ execinfo explicit_bzero faccessat
@@ -38,7 +38,8 @@ GNULIB_MODULES='
   getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog
   ieee754-h ignore-value intprops largefile lstat
   manywarnings memmem-simple memrchr minmax mkostemp mktime nstrftime
-  pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat regex
+  pathmax pipe2 pselect pthread_sigmask putenv
+  qcopy-acl readlink readlinkat regex
   sig2str socklen stat-time std-gnu11 stdalign stddef stdio
   stpcpy strnlen strtoimax symlink sys_stat sys_time
   tempname time time_r time_rz timegm timer-time timespec-add timespec-sub

lib-src/emacsclient.c

@@ -74,6 +74,7 @@ char *w32_getenv (const char *);
 #include <signal.h>
 #include <stdarg.h>
 #include <stddef.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -82,6 +83,7 @@ char *w32_getenv (const char *);
 #include <dosname.h>
 #include <intprops.h>
 #include <min-max.h>
+#include <pathmax.h>
 #include <unlocked-io.h>
 
 /* Work around GCC bug 88251.  */
@@ -238,6 +240,17 @@ char *get_current_dir_name (void);
 char *
 get_current_dir_name (void)
 {
+  /* The maximum size of a directory name, including the terminating NUL.
+     Leave room so that the caller can append a trailing slash.  */
+  ptrdiff_t dirsize_max = min (PTRDIFF_MAX, SIZE_MAX) - 1;
+
+  /* The maximum size of a buffer for a file name, including the
+     terminating NUL.  This is bounded by PATH_MAX, if available.  */
+  ptrdiff_t bufsize_max = dirsize_max;
+#ifdef PATH_MAX
+  bufsize_max = min (bufsize_max, PATH_MAX);
+#endif
+
   char *buf;
   struct stat dotstat, pwdstat;
   /* If PWD is accurate, use it instead of calling getcwd.  PWD is
@@ -245,15 +258,12 @@ get_current_dir_name (void)
      parent directory is searchable but not readable.  */
   char const *pwd = egetenv ("PWD");
   if (pwd
-      && (IS_DIRECTORY_SEP (*pwd) || (*pwd && IS_DEVICE_SEP (pwd[1])))
+      && (pwdlen = strnlen (pwd, bufsize_max)) < bufsize_max
+      && IS_DIRECTORY_SEP (pwd[pwdlen && IS_DEVICE_SEP (pwd[1]) ? 2 : 0])
       && stat (pwd, &pwdstat) == 0
       && stat (".", &dotstat) == 0
       && dotstat.st_ino == pwdstat.st_ino
-      && dotstat.st_dev == pwdstat.st_dev
-# ifdef MAXPATHLEN
-      && strlen (pwd) < MAXPATHLEN
-# endif
-      )
+      && dotstat.st_dev == pwdstat.st_dev)
     {
       buf = xmalloc (strlen (pwd) + 1);
       strcpy (buf, pwd);

lib/gnulib.mk.in

@@ -120,6 +120,7 @@
 #  mkostemp \
 #  mktime \
 #  nstrftime \
+#  pathmax \
 #  pipe2 \
 #  pselect \
 #  pthread_sigmask \
@@ -1076,6 +1077,7 @@ gl_GNULIB_ENABLED_getdtablesize = @gl_GNULIB_ENABLED_getdtablesize@
 gl_GNULIB_ENABLED_getgroups = @gl_GNULIB_ENABLED_getgroups@
 gl_GNULIB_ENABLED_malloca = @gl_GNULIB_ENABLED_malloca@
 gl_GNULIB_ENABLED_open = @gl_GNULIB_ENABLED_open@
+gl_GNULIB_ENABLED_pathmax = @gl_GNULIB_ENABLED_pathmax@
 gl_GNULIB_ENABLED_strtoll = @gl_GNULIB_ENABLED_strtoll@
 gl_LIBOBJS = @gl_LIBOBJS@
 gl_LTLIBOBJS = @gl_LTLIBOBJS@
@@ -2110,9 +2112,7 @@ endif
 ## begin gnulib module pathmax
 ifeq (,$(OMIT_GNULIB_MODULE_pathmax))
 
-ifneq (,$(gl_GNULIB_ENABLED_pathmax))
 
-endif
 EXTRA_DIST += pathmax.h
 
 endif

m4/gnulib-comp.m4

@@ -347,6 +347,7 @@ AC_DEFUN([gl_INIT],
   gl_TIME_MODULE_INDICATOR([mktime])
   gl_MULTIARCH
   gl_FUNC_GNU_STRFTIME
+  gl_PATHMAX
   gl_FUNC_PIPE2
   gl_UNISTD_MODULE_INDICATOR([pipe2])
   gl_FUNC_PSELECT
@@ -468,7 +469,6 @@ AC_DEFUN([gl_INIT],
   gl_gnulib_enabled_5264294aa0a5557541b53c8c741f7f31=false
   gl_gnulib_enabled_open=false
   gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7=false
-  gl_gnulib_enabled_pathmax=false
   gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c=false
   gl_gnulib_enabled_strtoll=false
   gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec=false
@@ -620,13 +620,6 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7=true
     fi
   }
-  func_gl_gnulib_m4code_pathmax ()
-  {
-    if ! $gl_gnulib_enabled_pathmax; then
-      gl_PATHMAX
-      gl_gnulib_enabled_pathmax=true
-    fi
-  }
   func_gl_gnulib_m4code_6099e9737f757db36c47fa9d9f02e88c ()
   {
     if ! $gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c; then
@@ -654,9 +647,6 @@ AC_DEFUN([gl_INIT],
   if test $HAVE_CANONICALIZE_FILE_NAME = 0 || test $REPLACE_CANONICALIZE_FILE_NAME = 1; then
     func_gl_gnulib_m4code_malloca
   fi
-  if test $HAVE_CANONICALIZE_FILE_NAME = 0 || test $REPLACE_CANONICALIZE_FILE_NAME = 1; then
-    func_gl_gnulib_m4code_pathmax
-  fi
   if test $HAVE_FACCESSAT = 0 || test $REPLACE_FACCESSAT = 1; then
     func_gl_gnulib_m4code_260941c0e5dc67ec9e87d1fb321c300b
   fi
@@ -720,7 +710,6 @@ AC_DEFUN([gl_INIT],
   AM_CONDITIONAL([gl_GNULIB_ENABLED_5264294aa0a5557541b53c8c741f7f31], [$gl_gnulib_enabled_5264294aa0a5557541b53c8c741f7f31])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_open], [$gl_gnulib_enabled_open])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_03e0aaad4cb89ca757653bd367a6ccb7], [$gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7])
-  AM_CONDITIONAL([gl_GNULIB_ENABLED_pathmax], [$gl_gnulib_enabled_pathmax])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c], [$gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_strtoll], [$gl_gnulib_enabled_strtoll])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_682e609604ccaac6be382e4ee3a4eaec], [$gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec])

src/sysdep.c

@@ -30,6 +30,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <unistd.h>
 
 #include <c-ctype.h>
+#include <pathmax.h>
 #include <utimens.h>
 
 #include "lisp.h"
@@ -262,10 +263,10 @@ get_current_dir_name_or_unreachable (void)
   ptrdiff_t dirsize_max = min (PTRDIFF_MAX, SIZE_MAX) - 1;
 
   /* The maximum size of a buffer for a file name, including the
-     terminating NUL.  This is bounded by MAXPATHLEN, if available.  */
+     terminating NUL.  This is bounded by PATH_MAX, if available.  */
   ptrdiff_t bufsize_max = dirsize_max;
-#ifdef MAXPATHLEN
-  bufsize_max = min (bufsize_max, MAXPATHLEN);
+#ifdef PATH_MAX
+  bufsize_max = min (bufsize_max, PATH_MAX);
 #endif
 
 # if HAVE_GET_CURRENT_DIR_NAME && !BROKEN_GET_CURRENT_DIR_NAME