Carry the gnulib getcwd backport as a patch

Commit

  e2fc52e7457 ("Fix PR gdb/23558: Use system's 'getcwd' when cross-compiling GDB")

backported some changes from a future gnulib version to our import.
However, this means that every time someone wants to change our gnulib
import (e.g. add a module), they must make sure not to include that
backported change.  It also means that someone running the
update-gnulib.sh script without changes will get some diffs and wonder
why.

Instead, I suggest we carry that backport as a patch applied by the
update-gnulib.sh script after running the import tool.  It will make it
clear what backport or local modification we have and should make
running update-gnulib.sh give a reproducible result.

There is a hunk in the configure file in this patch, this is because the
commit that backported the getcwd bits didn't include the re-generated
configure.

Note: you'll need this patch as well to get deterministic results:

  Generate aclocal-m4-deps.mk more deterministically and portably.
  https://sourceware.org/ml/gdb-patches/2018-09/msg00643.html

gdb/ChangeLog:

	* patches/0001-Fix-PR-gdb-23558-Use-system-s-getcwd-when-cross-comp.patch:
	New file.
	* update-gnulib.sh: Apply patch.
	* configure: Re-generate.

4 files changed, 103 insertions, 3 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0a0033a..004a253 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-18  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* patches/0001-Fix-PR-gdb-23558-Use-system-s-getcwd-when-cross-comp.patch:
+	New file.
+	* update-gnulib.sh: Apply patch.
+	* configure: Re-generate.
+
 2018-09-18  John Baldwin  <jhb@FreeBSD.org>
 
 	* infcmd.c (_initialize_infcmd): Remove "running" from "info proc"
diff --git a/gdb/gnulib/configure b/gdb/gnulib/configure
index 5fd52d4..dc6c5b6 100644
--- a/gdb/gnulib/configure
+++ b/gdb/gnulib/configure
@@ -17696,10 +17696,22 @@ else
   # Arrange for deletion of the temporary directory this test creates.
      ac_clean_files="$ac_clean_files confdir3"
           if test "$cross_compiling" = yes; then :
-  case "$host_os" in
-       aix*) gl_cv_func_getcwd_path_max='no, it has the AIX bug';;
-       *) gl_cv_func_getcwd_path_max=no;;
+  # Cross-compilation guesses:
+     case "$host_os" in
+       aix*) # On AIX, it has the AIX bug.
+         gl_cv_func_getcwd_path_max='no, it has the AIX bug' ;;
+       gnu*) # On Hurd, it is 'yes'.
+         gl_cv_func_getcwd_path_max=yes ;;
+       linux* | kfreebsd*)
+         # On older Linux+glibc it's 'no, but it is partly working',
+         # on newer Linux+glibc it's 'yes'.
+         # On Linux+musl libc, it's 'no, but it is partly working'.
+         # On kFreeBSD+glibc, it's 'no, but it is partly working'.
+         gl_cv_func_getcwd_path_max='no, but it is partly working' ;;
+       *) # If we don't know, assume the worst.
+         gl_cv_func_getcwd_path_max=no ;;
      esac
+
 else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
diff --git a/gdb/gnulib/patches/0001-Fix-PR-gdb-23558-Use-system-s-getcwd-when-cross-comp.patch b/gdb/gnulib/patches/0001-Fix-PR-gdb-23558-Use-system-s-getcwd-when-cross-comp.patch
new file mode 100644
index 0000000..1d8cdf6
--- /dev/null
+++ b/gdb/gnulib/patches/0001-Fix-PR-gdb-23558-Use-system-s-getcwd-when-cross-comp.patch
@@ -0,0 +1,69 @@
+From a7447215cdc492a077732420a3f0db6d48b34d51 Mon Sep 17 00:00:00 2001
+From: Sergio Durigan Junior <sergiodj@redhat.com>
+Date: Mon, 10 Sep 2018 12:52:04 -0400
+Subject: [PATCH] Fix PR gdb/23558: Use system's 'getcwd' when cross-compiling
+ GDB
+
+This is a backport of a gnulib fix for the following bug:
+
+  https://sourceware.org/bugzilla/show_bug.cgi?id=23558
+
+The problem reported there is about the replacement of 'getcwd' when
+cross-compiling GDB.  With our current gnulib copy, the mechanism for
+deciding whether to use the system's 'getcwd' or gnulib's version is
+too simplistic and pessimistic, so when cross-compiling we always end
+up using gnulib's version, which has a limitation: it cannot handle
+the situation when the parent directory doesn't have read permissions.
+
+The solution is to backport the following gnulib commit:
+
+  commit a96d2e67052c879b1bcc5bc461722beac75fc372
+  Author: Bruno Haible <bruno@clisp.org>
+  Date:   Thu Aug 23 21:13:19 2018 +0200
+
+      getcwd: Add cross-compilation guesses.
+
+gdb/ChangeLog:
+2018-09-10  Sergio Durigan Junior  <sergiodj@redhat.com>
+
+	PR gdb/23555
+	PR gdb/23558
+	* gnulib/import/m4/getcwd-path-max.m4: Add cross-compilation
+	guesses.
+---
+ gdb/gnulib/import/m4/getcwd-path-max.m4 | 20 ++++++++++++++++----
+ 1 file changed, 16 insertions(+), 4 deletions(-)
+
+diff --git a/gdb/gnulib/import/m4/getcwd-path-max.m4 b/gdb/gnulib/import/m4/getcwd-path-max.m4
+index 2531ccff65c..90bbc77dea1 100644
+--- a/gdb/gnulib/import/m4/getcwd-path-max.m4
++++ b/gdb/gnulib/import/m4/getcwd-path-max.m4
+@@ -209,9 +209,21 @@ main ()
+      32) gl_cv_func_getcwd_path_max='yes, but with shorter paths';;
+      *) gl_cv_func_getcwd_path_max=no;;
+      esac],
+-    [case "$host_os" in
+-       aix*) gl_cv_func_getcwd_path_max='no, it has the AIX bug';;
+-       *) gl_cv_func_getcwd_path_max=no;;
+-     esac])
++    [# Cross-compilation guesses:
++     case "$host_os" in
++       aix*) # On AIX, it has the AIX bug.
++         gl_cv_func_getcwd_path_max='no, it has the AIX bug' ;;
++       gnu*) # On Hurd, it is 'yes'.
++         gl_cv_func_getcwd_path_max=yes ;;
++       linux* | kfreebsd*)
++         # On older Linux+glibc it's 'no, but it is partly working',
++         # on newer Linux+glibc it's 'yes'.
++         # On Linux+musl libc, it's 'no, but it is partly working'.
++         # On kFreeBSD+glibc, it's 'no, but it is partly working'.
++         gl_cv_func_getcwd_path_max='no, but it is partly working' ;;
++       *) # If we don't know, assume the worst.
++         gl_cv_func_getcwd_path_max=no ;;
++     esac
++    ])
+   ])
+ ])
+-- 
+2.19.0
+
diff --git a/gdb/gnulib/update-gnulib.sh b/gdb/gnulib/update-gnulib.sh
index 327b37f..09933ab 100755
--- a/gdb/gnulib/update-gnulib.sh
+++ b/gdb/gnulib/update-gnulib.sh
@@ -158,6 +158,18 @@ if [ $? -ne 0 ]; then
    exit 1
 fi
 
+# Apply our local patches.
+apply_patches ()
+{
+    patch -p3 -f -i "$1"
+    if [ $? -ne 0 ]; then
+        echo "Failed to apply some patches.  Aborting."
+        exit 1
+    fi
+}
+
+apply_patches "patches/0001-Fix-PR-gdb-23558-Use-system-s-getcwd-when-cross-comp.patch"
+
 # Regenerate all necessary files...
 aclocal -Iimport/m4 &&
 autoconf &&