On Feb 9 12:40, Corinna Vinschen wrote: > On Feb 9 11:29, David Allsopp wrote: > > > Apart from that, not only Cygwin DLLs but also the Windows system DLLs > > > are all loaded and relocated to the area beyond 0x1:80000000, so > > > relocation beyond the 32 bit address space is no generic problem in > > > Windows. Why isn't that possible in FlexDLL? I don't understand this. > > > To me this looks like a bug in FlexDLL, not a requirement to let certain > > > DLLs slip through the cracks. > > > > There's a more full explanation of what and why for flexdll here: > > https://github.com/alainfrisch/flexdll/blob/master/README.md. I > > believe it's not unrelated to some of the black magic going on in > > Cygwin's autoload.cc, but without (at least at the moment), quite as > > much self-modifying code. > > [...] > > I guess one can argue over whether that's a bug or a limitation, but > > the problem we face is that we can engineer it so that our DLLs and > > executables are within a 2GB range (having looked again at this in > > even more detail, we could just as readily do this with addresses > > > 0x200000000), but we still run the risk of rebase messing up the DLLs. > > > > However, we'll scratch our heads some more on possible alternative > > solutions, since having a flag for DLLs which says "keep us within a > > 2GB range somewhere" sounds even more less likely to get merged than > > my previous suggestion. > > Two points: > > - You are aware that the main executable of 64 bit Cygwin processes are > loaded to 0x1:00400000, right? The 2 GB offset problem is already > imminent.
...and you must not use the 0x0:80000000 - 0x1:00000000 area because that's reserved for thread stacks. To clarify, the full layout requirements: - 0x0:00000000 - 0x0:80000000 Windows - 0x0:80000000 - 0x1:00000000 Cygwin pthreads (including main thread) - 0x1:00000000 - 0x1:80000000 Executable - 0x1:80000000 - 0x2:00000000 Cygwin DLL - 0x2:00000000 - 0x4:00000000 Rebased DLLs - 0x4:00000000 - 0x6:00000000 Non-rebased DLLs (hashed default addresses generated by binutils ld with -auto-image-based (default on Cygwin)) - 0x6:00000000 Start Address Heap, growing upwards - 0x8:00000000 - 0x700:00000000 Mmaps, allocated downwards - 0x700:00000000 and beyond Windows Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
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