Add Makefile support for debugging CPython

And some install instructions on how to get a pre-built debug build,
and to put the sources where the Pyston make system expects them.

Makefile

@@ -869,6 +869,10 @@ runpy_%: %.py ext_python
 	PYTHONPATH=test/test_extension/build/lib.linux-x86_64-2.7 python $<
 $(call make_search,runpy_%)
 
+dbgpy_%: %.py ext_pythondbg
+	export PYTHON_VERSION=$$(python2.7-dbg -V 2>&1 | awk '{print $$2}'); PYTHONPATH=test/test_extension/build/lib.linux-x86_64-2.7-pydebug $(GDB) --ex "dir $(DEPS_DIR)/python-src/python2.7-$$PYTHON_VERSION/debian" $(GDB_CMDS) --args python2.7-dbg $<
+$(call make_search,dbgpy_%)
+
 # "kill valgrind":
 kv:
 	ps aux | awk '/[v]algrind/ {print $$2}' | xargs kill -9; true
@@ -991,9 +995,11 @@ ext_pyston_selfhost_release: pyston_release $(TEST_EXT_MODULE_NAMES:%=$(TEST_DIR
 	cd $(TEST_DIR)/test_extension; DISTUTILS_DEBUG=1 time ../../pyston_release setup.py build
 	cd $(TEST_DIR)/test_extension; ln -sf $(TEST_EXT_MODULE_NAMES:%=build/lib.unknown-2.7/%.pyston.so) .
 
-.PHONY: ext_python
+.PHONY: ext_python ext_pythondbg
 ext_python: $(TEST_EXT_MODULE_NAMES:%=$(TEST_DIR)/test_extension/*.c)
 	cd $(TEST_DIR)/test_extension; python setup.py build
+ext_pythondbg: $(TEST_EXT_MODULE_NAMES:%=$(TEST_DIR)/test_extension/*.c)
+	cd $(TEST_DIR)/test_extension; python2.7-dbg setup.py build
 
 $(FROM_CPYTHON_SRCS:.c=.o): %.o: %.c $(BUILD_SYSTEM_DEPS)
 	$(ECHO) Compiling C file to $@

docs/INSTALLING.md

@@ -248,36 +248,19 @@ download from http://code.google.com/p/gperftools/downloads/list
 standard ./configure, make, make install
 ```
 
-### ninja-based LLVM build
+### Debug build of CPython
 
-Ninja is supposed to be faster than make; I've only tried it very briefly, and it does seem to be faster when modifying LLVM files.  May or may not be worth using; thought I'd jot down my notes though:
+Having a debug-enabled CPython can be useful for debugging issues with our extension modules.  To get it set up:
 
-You may or may not need a more-recent version of ninja than your package manager provides:
 ```
+sudo apt-get install python2.7-dbg
 cd ~/pyston_deps
-git clone https://github.com/martine/ninja.git
-cd ninja
-git checkout v1.4.0
-./bootstrap.py
-```
-
-```
-cd ~/pyston_deps
-wget http://www.cmake.org/files/v3.0/cmake-3.0.0.tar.gz
-tar zxvf cmake-3.0.0.tar.gz
-cd cmake-3.0.0
-./configure
-make -j4
-```
-
-```
-cd ~/pyston_deps
-mkdir llvm-trunk-cmake
-cd llvm-trunk-cmake
-CXX=g++ CC=gcc PATH=~/pyston_deps/gcc-4.8.2-install/bin:$PATH:~/pyston_deps/ninja CMAKE_MAKE_PROGRAM=~/pyston_deps/ninja/ninja ~/pyston_deps/cmake-3.0.0/bin/cmake ../llvm-trunk -G Ninja -DLLVM_TARGETS_TO_BUILD=host -DCMAKE_BUILD_TYPE=RELEASE -DLLVM_ENABLE_ASSERTIONS=ON
-~/pyston_deps/ninja/ninja # runs in parallel
+mkdir python-src
+cd python-src
+apt-get source python2.7-dbg
 ```
 
+Then, run `make dbgpy_TESTNAME` and it will launch the test under gdb.  There's also a [wiki page](https://wiki.python.org/moin/DebuggingWithGdb) with some extra Python-specific GDB commands.
 
 # (Experimental) CMake build system