On 25/05/2024 22:55, Martin Wege via Cygwin wrote:
Hello,
Does Cygwin or Win32 have something like LD_PRELOAD, so I can
override/substitute functions in a DLL or EXE, like it is common for
UNIX/Linux ELF shared libraries?
This is not generally available on Win32, due to limitations of the PE
file format.
(basically, the import table lists symbols which are imported, and where
they are imported from, so the module (shared library or executable)
which provides a given symbol is determined when the module is *linked*,
not when it is loaded.
However, when googling "cygwin LD_PRELOAD" (which surely you must have
done before asking this question?) I discover that there's some voodoo
in the cygwin DLL (hookapi.cc) which claims to do something like that,
but it seems (i) this requires the preloaded DLL to explicitly hook
functions it's overriding, and (ii) maybe only works on functions
imported by the running executable.
It would be nice to have some documentation for that, and/or a simple
example which could serve as a testcase.
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