Oliver's /dev/null replacement

How can you get the instance handle of a DLL, if the function that you write is linked into the DLL but you have no access to hInstance from the DllMain? GetModuleHandle only allows you to get the handle to the module that created the current process – in case you don’t know the path to the module (which we assume).

So let’s say you want to somehow get the instance handle but can’t use DllMain for some reason. The solution is in using VirtualQuery. We abuse a feature of static variables in PE executables. Unlike the usual stack variable (and various other options), those are located within the loaded image of the DLL. Here’s how it looks.

HMODULE GetMyModuleHandle()
{
    static int s_somevar = 0;
    MEMORY_BASIC_INFORMATION mbi;
    if(!::VirtualQuery(&s_somevar, &mbi, sizeof(mbi)))
    {
        return NULL;
    }
    return static_cast(mbi.AllocationBase);
}

If you have linked the CRT of Visual C++, you can get away with a simple reinterpret_cast<HMODULE>(&__ImageBase)

So don’t sweat it, as most people do whenever I quiz them about this

// Oliver

I’ve just replaced my little shell script that was helping me to update the hash files inside my postfix configuration. While before I had hardcoded the paths/names, they are now simply fetched by means of find. In addition to the old capabilities, the new make file will also copy any files required inside the chrooted /etc, if they aren’t up-do-date. Since make works by means of timestamps of the targets, this is easily achieved.

Here’s how it looks (stripped the “intro” of the make file, though).

config-files := $(shell find /var/spool/postfix/etc/ -type f)
hash-files   := $(shell find $(CURDIR) -name '*.hash')
hashdb-files := $(addsuffix .db,$(hash-files))

.PHONY: all
all: $(hashdb-files) $(config-files)
    newaliases
    postfix check
    postfix reload

/var/spool/postfix/etc/%: /etc/%
    cp --preserve=timestamps $(patsubst /var/spool/postfix%,%,$@) $@

%.hash.db: %.hash
    postmap $(patsubst %.db,%,$@)
    @chown root:postfix $@ $(patsubst %.db,%,$@)
    @chmod u=rwX,g=r,o= $@ $(patsubst %.db,%,$@)
ifeq ($(filter $(MAKECMDGOALS),all rebuild),)
    postfix check
    postfix reload
endif

.PHONY: info
info:
    -@echo "config-files = $(config-files)"
    -@echo "hash-files   = $(hash-files)"
    -@echo "hashdb-files = $(hashdb-files)"

.PHONY: rebuild
rebuild: clean all

.PHONY: clean
clean:
    -@echo "Cleaning $(CURDIR) ..."
    -@rm -f $(hashdb-files)

You can download it here.

// Oliver

Everyone loved Visual Studio 6 and many people continued using it despite the availability of VS 2002, 2003, 2005 and 2008. Now, I saw Microsoft promise on some website that version 2010 will be the new version 6. Somehow I don’t think so. Apart from it coming even bulkier and being slower than VS 2005 (my favorite), it required two reboots during installation for the beta version.

Maybe the next one will be better?

// Oliver

PS: Oh, and I noticed that it was moved to MSBuild as project file format, which causes DDKWizard to fail.