| # |
| # 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 |
