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 tested on an AMD64 running
Ubuntu 14.04 and an x86 VM running Fedora 24.

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 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 native builds and a cross build using a Beaglebone
Black running Debian, with the build system's filesystem shared with the board
through NFS.

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

	* INSTALL: Regenerated.
	* Makeconfig: Add comments and whitespace to make the control flow
	clearer.
	(+link-printers-tests, +link-pie-printers-tests, CFLAGS-printers-tests,
	installed-rtld-LDFLAGS, built-rtld-LDFLAGS, link-libc-rpath,
	link-libc-tests-after-rpath-link, link-libc-printers-tests): New.
	(rtld-LDFLAGS, rtld-tests-LDFLAGS, link-libc-tests-rpath-link,
	link-libc-tests): Use the new variables as required.
	* Makerules ($(py-const)): New rule.
	generated: Add $(py-const).
	* README.pretty-printers: New file.
	* Rules (tests-printers-programs, tests-printers-out, py-env): New.
	(others): Depend on $(py-const).
	(tests): Depend on $(tests-printers-programs) or $(tests-printers-out),
	as required.  Pass $(tests-printers) to merge-test-results.sh.
	* manual/install.texi: Add requirements for testing the pretty printers.
	* nptl/Makefile (gen-py-const-headers, pretty-printers, tests-printers,
	CFLAGS-test-mutexattr-printers.c CFLAGS-test-mutex-printers.c,
	CFLAGS-test-condattr-printers.c, CFLAGS-test-cond-printers.c,
	CFLAGS-test-rwlockattr-printers.c CFLAGS-test-rwlock-printers.c,
	tests-printers-libs): Define.
	* nptl/nptl-printers.py: New file.
	* nptl/nptl_lock_constants.pysym: Likewise.
	* nptl/test-cond-printers.c: Likewise.
	* nptl/test-cond-printers.py: Likewise.
	* nptl/test-condattr-printers.c: Likewise.
	* nptl/test-condattr-printers.py: Likewise.
	* nptl/test-mutex-printers.c: Likewise.
	* nptl/test-mutex-printers.py: Likewise.
	* nptl/test-mutexattr-printers.c: Likewise.
	* nptl/test-mutexattr-printers.py: Likewise.
	* nptl/test-rwlock-printers.c: Likewise.
	* nptl/test-rwlock-printers.py: Likewise.
	* nptl/test-rwlockattr-printers.c: Likewise.
	* nptl/test-rwlockattr-printers.py: Likewise.
	* scripts/gen-py-const.awk: Likewise.
	* scripts/test_printers_common.py: Likewise.
	* scripts/test_printers_exceptions.py: Likewise.

1 files changed, 46 insertions, 0 deletions

diff --git a/Makerules b/Makerules
index e865782..7214b2b 100644
--- a/Makerules
+++ b/Makerules
@@ -210,6 +210,52 @@ sed-remove-dotdot := -e 's@  *\([^ 	\/$$][^ 	\]*\)@ $$(..)\1@g' \
 		     -e 's@^\([^ 	\/$$][^ 	\]*\)@$$(..)\1@g'
 endif
 
+ifdef gen-py-const-headers
+# We'll use a static pattern rule to match .pysym files with their
+# corresponding generated .py files.
+# The generated .py files go in the submodule's dir in the glibc build dir.
+py-const-files := $(patsubst %.pysym,%.py,$(gen-py-const-headers))
+py-const-dir := $(objpfx)
+py-const := $(addprefix $(py-const-dir),$(py-const-files))
+py-const-script := $(..)scripts/gen-py-const.awk
+
+# This is a hack we use to generate .py files with constants for Python
+# pretty printers.  It works the same way as gen-as-const.
+# See scripts/gen-py-const.awk for details on how the awk | gcc mechanism
+# works.
+#
+# $@.tmp and $@.tmp2 are temporary files we use to store the partial contents
+# of the target file.  We do this instead of just writing on $@ because, if the
+# build process terminates prematurely, re-running Make wouldn't run this rule
+# since Make would see that the target file already exists (despite it being
+# incomplete).
+#
+# The sed line replaces "@name@SOME_NAME@value@SOME_VALUE@" strings from the
+# output of 'gcc -S' with "SOME_NAME = SOME_VALUE" strings.
+# The '-n' option, combined with the '/p' command, makes sed output only the
+# modified lines instead of the whole input file.  The output is redirected
+# to a .py file; we'll import it in the pretty printers file to read
+# the constants generated by gen-py-const.awk.
+# The regex has two capturing groups, for SOME_NAME and SOME_VALUE
+# respectively.  Notice SOME_VALUE may be prepended by a special character,
+# depending on the assembly syntax (e.g. immediates are prefixed by a '$'
+# in AT&T x86, and by a '#' in ARM).  We discard it using a complemented set
+# before the second capturing group.
+$(py-const): $(py-const-dir)%.py: %.pysym $(py-const-script) \
+	     $(common-before-compile)
+	$(make-target-directory)
+	$(AWK) -f $(py-const-script) $< \
+	       | $(CC) -S -o $@.tmp $(CFLAGS) $(CPPFLAGS) -x c -
+	echo '# GENERATED FILE\n' > $@.tmp2
+	echo '# Constant definitions for pretty printers.' >> $@.tmp2
+	echo '# See gen-py-const.awk for details.\n' >> $@.tmp2
+	sed -n -r 's/^.*@name@([^@]+)@value@[^[:xdigit:]Xx-]*([[:xdigit:]Xx-]+)@.*/\1 = \2/p' \
+	    $@.tmp >> $@.tmp2
+	mv -f $@.tmp2 $@
+	rm -f $@.tmp
+
+generated += $(py-const)
+endif  # gen-py-const-headers
 
 ifdef gen-as-const-headers
 # Generating headers for assembly constants.