From 8664d4b725eeb9c5845fa36331f2184d2c1f8596 Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Fri, 17 Jan 2020 19:13:15 +0100
Subject: [PATCH] Abort configure immediately if building GDB in tree

The move of gnulib to the top src directory is causing the GDB build
to break if configured in tree. We hope to lift that limitation at
some point but, in the meantime, this commit allows us to abort
the initial configure right away with a clear error message should
the user attempt to build in tree.

ChangeLog:

        * configure.ac: Abort the build with an error if trying to build
        GDB in tree.
        * configure: Regenerate.
---
 configure    | 17 +++++++++++++++++
 configure.ac | 17 +++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/configure b/configure
index 6a9719f6091..7168a4e90e0 100755
--- a/configure
+++ b/configure
@@ -2279,6 +2279,23 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
+if test x"${enable_gdb}" != x"no"; then
+  # For this branch, we do not support building GDB in-tree.
+  # Try to detect whether we are in this situation or not by
+  # searching for a couple of known files in the source directory.
+  if test -f gnulib/update-gnulib.sh -a -f gdb/ChangeLog; then
+    as_fn_error $? "GDB must be configured and built in a directory separate from its sources.
+
+To do so, create a dedicated directory for your GDB build and invoke
+the configure script from that directory:
+
+      $ mkdir build
+      $ cd build
+      $ <full path to your sources>/gdb-VERSION/configure [etc...]
+      $ make" "$LINENO" 5
+  fi
+fi
+
 progname=$0
 # if PWD already has a value, it is probably wrong.
 if test -n "$PWD" ; then PWD=`${PWDCMD-pwd}`; fi
diff --git a/configure.ac b/configure.ac
index 7433badc217..e5ca1eaa57a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -33,6 +33,23 @@ m4_include([config/isl.m4])
 AC_INIT(move-if-change)
 AC_DISABLE_OPTION_CHECKING
 
+if test x"${enable_gdb}" != x"no"; then
+  # For this branch, we do not support building GDB in-tree.
+  # Try to detect whether we are in this situation or not by
+  # searching for a couple of known files in the source directory.
+  if test -f gnulib/update-gnulib.sh -a -f gdb/ChangeLog; then
+    AC_MSG_ERROR([GDB must be configured and built in a directory separate from its sources.
+
+To do so, create a dedicated directory for your GDB build and invoke
+the configure script from that directory:
+
+      $ mkdir build
+      $ cd build
+      $ <full path to your sources>/gdb-VERSION/configure [[etc...]]
+      $ make])
+  fi
+fi
+
 progname=$0
 # if PWD already has a value, it is probably wrong.
 if test -n "$PWD" ; then PWD=`${PWDCMD-pwd}`; fi
-- 
2.17.1