mozglue/crt/Makefile.in
author Mike Hommey <mh+mozilla@glandium.org>
Tue, 26 May 2015 15:48:21 +0900
changeset 281896 d3b7794f08af91f2a7afb77e43621002e06d3bfc
parent 237374 7c2f1416473fc4c03f96299a68ba869de9467b48
child 343553 f378a56b25ce2a2997b263c1857629f3f18d7400
permissions -rw-r--r--
Bug 1168291 - Install mozcrt.lib instead of mozglue.lib in the SDK. r=mshal, a=lmandel When building with MOZ_CRT (which is more or less the default when building on Windows with MSVC2013), building e.g. XPCOM components requires linking against mozcrt.lib, so it needs to be shipped in the SDK. On the other hand, mozglue.lib, which is currently shipped, is not useful because it lacks the necessary hacks from mozcrt.lib avoiding crashes for memory allocator mismatch.

#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

# Roll our own custom logic here for the import library

###############################################################################
#
# Linking Mozilla itself to jemalloc is not particularly difficult.  To do this
# we avoid linking directly to the Microsoft-provided CRT import libraries.
# Instead, we link to our own import library which we generate here.  To
# replace the CRT's malloc/free/other memory management symbols we export
# our own versions out of jemalloc.dll.  We then take the import library that
# the compiler generates for jemalloc.dll and combine it with the MS CRT import
# libraries.  We put our library on the command line first, and the CRT symbols
# are discarded in favor of our versions!
#
# Unfortunately that was too easy.  The CRT import library is not a standard
# import library that contains a list of symbols and whatnot.  It also includes
# object files that are linked into generated programs.  One of these,
# crtdll.obj is (as one might expect) linked into all DLLs that link against
# the CRT.  This file does things like run static C++ constructors when the
# DLL is attached, call DllMain, etc.
#
# In the CRT source all malloc/free calls are made to malloc_crt and free_crt.
# In debug builds these are both defined to malloc_dbg and free_dbg.  In opt
# builds malloc_crt is an actual function, implemented and exposed from the
# CRT.  free_crt is, however, defined to be just plain old free.  This works
# fine inside the CRT where malloc_crt and free operate on the same heap.
# Outside the CRT malloc_crt is in the CRT's heap, but free is in jemalloc's
# heap.  This causes much pain at shutdown :-(
#
# The obvious solution here is to override malloc_crt too.  Unfortunately,
# that doesn't work because the CRT expects to be able to call msize on this
# piece of memory deep inside the CRT, which will fail because it'll call the
# CRT's msize on a pointer in jemalloc's heap.
#
# Our solution to this is quite devious.  We take apart the CRT's import lib
# and remove the problematic object file.  We then poke at the object file's
# symbol table and replace '__imp__free' (which means grab free from some
# other DLL) with '__imp__frex'.  Then we define our own dummy no-op function
# in jemalloc.dll and export it as frex.  Then we put the CRT import lib
# back together with the patched crtdll.obj, glue it to the end of jemalloc's
# import library and link the rest of Mozilla to that.
#
# The result?  A binary that uses jemalloc, doesn't crash, and leaks a tiny
# amount of memory (32 words per DLL in the 2010 CRT) at shutdown.
#
###############################################################################

target:: mozcrt.lib
	$(INSTALL) $(IFLAGS2) mozcrt.lib $(DIST)/lib

# And finally combine that with the jemalloc import library to get an import
# library that has our malloc/free/etc and the CRT's everything else
mozcrt.lib: ../build/mozglue.lib msvc_modified.lib
	lib -OUT:$@ $^

# Put the fixed object file back in
msvc_modified.lib: msvc_removed.lib crtdll_fixed.obj
	lib -OUT:$@ $^

# Fix the object file
crtdll_fixed.obj: crtdll.obj
	$(PYTHON) $(srcdir)/fixcrt.py

# Find the path of crtdll.obj
CRTDLL_FULLPATH=$(subst \,\\,$(shell lib -list msvc_combined.lib | grep crtdll\\.obj))

# Remove the broken object file, only after we have extracted it
msvc_removed.lib: msvc_combined.lib crtdll.obj
	lib -OUT:$@ msvc_combined.lib -REMOVE:$(CRTDLL_FULLPATH)

# Extract the broken object file out of the combined library
crtdll.obj: msvc_combined.lib
	lib -OUT:$@ $^ -EXTRACT:$(CRTDLL_FULLPATH)

# Grab both CRT libraries and combine them into one library to simplify things
msvc_combined.lib:
	lib -OUT:$@ $(WIN32_CRT_LIBS)

# Normally, we'd use SDK_LIBRARY, but we can't because all the tricks above
# involve *not* defining the library in moz.build, so SDK_LIBRARY = True would
# not have the expected outcome.
SDK_FILES = mozcrt.lib
SDK_DEST = $(SDK_LIB_DIR)
SDK_TARGET = target
INSTALL_TARGETS += SDK