Add pretty printers for the NPTL lock types

This patch adds pretty printers for the following NPTL types:

- pthread_mutex_t
- pthread_mutexattr_t
- pthread_cond_t
- pthread_condattr_t
- pthread_rwlock_t
- pthread_rwlockattr_t

To load the pretty printers into your gdb session, do the following:

python
import sys
sys.path.insert(0, '/path/to/glibc/build/nptl/pretty-printers')
end

source /path/to/glibc/source/pretty-printers/nptl-printers.py

You can check which printers are registered and enabled by issuing the
'info pretty-printer' gdb command. Printers should trigger automatically when
trying to print a variable of one of the types mentioned above.

The printers are architecture-independent, and were manually tested on both
the gdb CLI and Eclipse CDT.

In order to work, the printers need to know the values of various flags that
are scattered throughout pthread.h and pthreadP.h as enums and #defines. Since
replicating these constants in the printers file itself would create a
maintenance burden, I wrote a script called gen-py-const.awk that Makerules uses
to extract the constants. This script is pretty much the same as gen-as-const.awk,
except it doesn't cast the constant values to 'long' and is thorougly documented.
The constants need only to be enumerated in a .pysym file, which is then referenced
by a Make variable called gen-py-const-headers.

As for the install directory, I discussed this with Mike Frysinger and Siddhesh
Poyarekar, and we agreed that it can be handled in a separate patch, and it shouldn't
block merging of this one.

In addition, I've written a series of test cases for the pretty printers.
Each lock type (mutex, condvar and rwlock) has two test programs, one for itself
and other for its related 'attributes' object. Each test program in turn has a
PExpect-based Python script that drives gdb and compares its output to the
expected printer's. The tests run on the glibc host, which is assumed to have
both gdb and PExpect; if either is absent the tests will fail with code 77
(UNSUPPORTED). For cross-testing you should use cross-test-ssh.sh as test-wrapper.
I've tested the printers on both a native build and a cross build using a Beaglebone
Black, with the build system's filesystem shared with the board through NFS.

Finally, I've written a README that explains all this and more.

Hopefully this should be good to go in now. Thanks.

ChangeLog:

2016-07-04  Martin Galvan  <martin.galvan@tallertechnologies.com>

	* Makeconfig (build-hardcoded-path-in-tests): Set to 'yes' for shared builds
	if tests-need-hardcoded-path is defined.
	(all-subdirs): Add pretty-printers.
	* Makerules ($(py-const)): New rule.
	* Rules (others): Add $(py-const), if defined.
	* nptl/Makefile (gen-py-const-headers): Define.
	* nptl/nptl-printers.py: New file.
	* nptl/nptl_lock_constants.pysym: Likewise.
	* pretty-printers/Makefile: Likewise.
	* pretty-printers/README: Likewise.
	* pretty-printers/test-condvar-attributes.c: Likewise.
	* pretty-printers/test-condvar-attributes.p: Likewise.
	* pretty-printers/test-condvar-printer.c: Likewise.
	* pretty-printers/test-condvar-printer.py: Likewise.
	* pretty-printers/test-mutex-attributes.c: Likewise.
	* pretty-printers/test-mutex-attributes.py: Likewise.
	* pretty-printers/test-mutex-printer.c: Likewise.
	* pretty-printers/test-mutex-printer.py: Likewise.
	* pretty-printers/test-rwlock-attributes.c: Likewise.
	* pretty-printers/test-rwlock-attributes.py: Likewise.
	* pretty-printers/test-rwlock-printer.c: Likewise.
	* pretty-printers/test-rwlock-printer.py: Likewise.
	* pretty-printers/test_common.py: Likewise.
	* scripts/gen-py-const.awk: Likewise.

1 files changed, 3 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index e2737d5f47..4f04dd43e8 100644
--- a/NEWS
+++ b/NEWS
@@ -47,6 +47,9 @@ Version 2.24
   direction of negative infinity.  These are currently enabled as GNU
   extensions.
 
+* Initial support is added for pretty printing of pthread variables in gdb.
+  See pretty-printers/README for details on how to use it.
+
 Security related changes:
 
 * An unnecessary stack copy in _nss_dns_getnetbyname_r was removed.  It