[commit] fix gdb+python build failure if using non-GNU sed

[Joel Brobecker <brobecker at adacore dot com>]

Hello,

Non-GNU sed do not like the '?' quantifier when used in a s/// regexp
that involve back-references, causing the build to fail when trying
to link with Python support. This fixes it by using the '*' quantifier
instead.

As explained in the extensive comment that I added, it's not ideal,
and matches invalid version strings (Eg. "-lpython2..7"), but should
not be a problem in practice.  I tried all kinds of variations in
an attempt to make it work while being as strict as before, but never
really succeeded.  I think that'll be good enough.

gdb/ChangeLog:

 	* configure.ac: Work around non-GNU sed limitation when computing
 	python version number.
 	* configure: Regenerate.

Tested on x86_64-linux by building GDB.  I tested the effect of this
on FreeBSD and Solaris by running the command manually.  Not tested
on Windows proper, yet, but I ran the same sort of manual experiment
on Solaris.

I checked it in already, without waiting for review, not because
I consider it obvious, but because it's very small, and should repair
a build failure for some users.

---
 gdb/ChangeLog    |    6 ++++++
 gdb/configure    |   17 ++++++++++++++++-
 gdb/configure.ac |   17 ++++++++++++++++-
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 84013cb..7e95941 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2011-02-02  Joel Brobecker  <brobecker@adacore.com>
+
+	* configure.ac: Work around non-GNU sed limitation when computing
+	python version number.
+	* configure: Regenerate.
+
 2011-02-01  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	Fix debug printing of TYPE_INSTANCE.
diff --git a/gdb/configure b/gdb/configure
index 5a6d0be..5ee5ce6 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -10658,8 +10658,23 @@ fi
 
   have_libpython=no
   if test "${have_python_config}" = yes; then
+    # Determine the Python version by extracting "-lpython<version>"
+    # part of the python_libs. <version> is usually X.Y with X and Y
+    # being decimal numbers, but can also be XY (seen on Windows).
+    #
+    # The extraction is performed using sed with a regular expression.
+    # Initially, the regexp used was using the '?' quantifier to make
+    # the dot in the version number optional.  Unfortunately, this
+    # does not work with non-GNU versions of sed because, because of
+    # what looks like a limitation (the '?' quantifier does not work
+    # with back-references).  We work around this limitation by using
+    # the '*' quantifier instead.  It means that, in theory, we might
+    # match unexpected version strings such as "-lpython2..7", but
+    # this seems unlikely in practice.  And even if that happens,
+    # an error will be triggered later on, when checking that version
+    # number.
     python_version=`echo " ${python_libs} " \
-                         | sed -e 's,^.* -l\(python[0-9]*[.]\?[0-9]*\).*$,\1,'`
+                         | sed -e 's,^.* -l\(python[0-9]*[.]*[0-9]*\).*$,\1,'`
     case "${python_version}" in
     python*)
 
diff --git a/gdb/configure.ac b/gdb/configure.ac
index 68b0838..d2b75f6 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -769,8 +769,23 @@ else
 
   have_libpython=no
   if test "${have_python_config}" = yes; then
+    # Determine the Python version by extracting "-lpython<version>"
+    # part of the python_libs. <version> is usually X.Y with X and Y
+    # being decimal numbers, but can also be XY (seen on Windows).
+    #
+    # The extraction is performed using sed with a regular expression.
+    # Initially, the regexp used was using the '?' quantifier to make
+    # the dot in the version number optional.  Unfortunately, this
+    # does not work with non-GNU versions of sed because, because of
+    # what looks like a limitation (the '?' quantifier does not work
+    # with back-references).  We work around this limitation by using
+    # the '*' quantifier instead.  It means that, in theory, we might
+    # match unexpected version strings such as "-lpython2..7", but
+    # this seems unlikely in practice.  And even if that happens,
+    # an error will be triggered later on, when checking that version
+    # number.
     python_version=`echo " ${python_libs} " \
-                         | sed -e 's,^.* -l\(python[[0-9]]*[[.]]\?[[0-9]]*\).*$,\1,'`
+                         | sed -e 's,^.* -l\(python[[0-9]]*[[.]]*[[0-9]]*\).*$,\1,'`
     case "${python_version}" in
     python*)
       AC_TRY_LIBPYTHON(${python_version}, have_libpython,
-- 
1.7.1