зеркало из https://github.com/mozilla/gecko-dev.git
82 строки
3.8 KiB
Makefile
82 строки
3.8 KiB
Makefile
#
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# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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# Roll our own custom logic here for the import library
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###############################################################################
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#
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# Linking Mozilla itself to jemalloc is not particularly difficult. To do this
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# we avoid linking directly to the Microsoft-provided CRT import libraries.
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# Instead, we link to our own import library which we generate here. To
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# replace the CRT's malloc/free/other memory management symbols we export
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# our own versions out of jemalloc.dll. We then take the import library that
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# the compiler generates for jemalloc.dll and combine it with the MS CRT import
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# libraries. We put our library on the command line first, and the CRT symbols
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# are discarded in favor of our versions!
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#
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# Unfortunately that was too easy. The CRT import library is not a standard
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# import library that contains a list of symbols and whatnot. It also includes
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# object files that are linked into generated programs. One of these,
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# crtdll.obj is (as one might expect) linked into all DLLs that link against
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# the CRT. This file does things like run static C++ constructors when the
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# DLL is attached, call DllMain, etc.
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#
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# In the CRT source all malloc/free calls are made to malloc_crt and free_crt.
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# In debug builds these are both defined to malloc_dbg and free_dbg. In opt
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# builds malloc_crt is an actual function, implemented and exposed from the
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# CRT. free_crt is, however, defined to be just plain old free. This works
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# fine inside the CRT where malloc_crt and free operate on the same heap.
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# Outside the CRT malloc_crt is in the CRT's heap, but free is in jemalloc's
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# heap. This causes much pain at shutdown :-(
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#
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# The obvious solution here is to override malloc_crt too. Unfortunately,
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# that doesn't work because the CRT expects to be able to call msize on this
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# piece of memory deep inside the CRT, which will fail because it'll call the
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# CRT's msize on a pointer in jemalloc's heap.
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#
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# Our solution to this is quite devious. We take apart the CRT's import lib
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# and remove the problematic object file. We then poke at the object file's
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# symbol table and replace '__imp__free' (which means grab free from some
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# other DLL) with '__imp__frex'. Then we define our own dummy no-op function
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# in jemalloc.dll and export it as frex. Then we put the CRT import lib
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# back together with the patched crtdll.obj, glue it to the end of jemalloc's
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# import library and link the rest of Mozilla to that.
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#
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# The result? A binary that uses jemalloc, doesn't crash, and leaks a tiny
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# amount of memory (32 words per DLL in the 2010 CRT) at shutdown.
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#
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###############################################################################
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target:: mozcrt.lib
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$(INSTALL) $(IFLAGS2) mozcrt.lib $(DIST)/lib
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# And finally combine that with the jemalloc import library to get an import
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# library that has our malloc/free/etc and the CRT's everything else
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mozcrt.lib: ../build/mozglue.lib msvc_modified.lib
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lib -OUT:$@ $^
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# Put the fixed object file back in
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msvc_modified.lib: msvc_removed.lib crtdll_fixed.obj
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lib -OUT:$@ $^
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# Fix the object file
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crtdll_fixed.obj: crtdll.obj
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$(PYTHON) $(srcdir)/fixcrt.py
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# Find the path of crtdll.obj
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CRTDLL_FULLPATH=$(subst \,\\,$(shell lib -list msvc_combined.lib | grep crtdll\\.obj))
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# Remove the broken object file, only after we have extracted it
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msvc_removed.lib: msvc_combined.lib crtdll.obj
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lib -OUT:$@ msvc_combined.lib -REMOVE:$(CRTDLL_FULLPATH)
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# Extract the broken object file out of the combined library
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crtdll.obj: msvc_combined.lib
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lib -OUT:$@ $^ -EXTRACT:$(CRTDLL_FULLPATH)
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# Grab both CRT libraries and combine them into one library to simplify things
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msvc_combined.lib:
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lib -OUT:$@ $(WIN32_CRT_LIBS)
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