Re: Question about the ldd output

[Brian Inglis <Brian.Inglis@SystematicSw.ab.ca>]

On 2019-07-08 12:00, Lavrentiev, Anton (NIH/NLM/NCBI) [C] via cygwin wrote:
> Well, I don't think there's anything special that Cygwin does to load executables, because these are essentially Windows processes, so they are loaded by Windows, first and foremost.
> 
> But it gets even weirder.  Below are two _consecutive!_ runs of ldd on the very same executable.  Why the output differs so drastically (including the unknown dlls all of a sudden)?
> 
> 1.
>         ntdll.dll => /cygdrive/c/WINDOWS/SYSTEM32/ntdll.dll (0x7ffc339d0000)
>         KERNEL32.DLL => /cygdrive/c/WINDOWS/System32/KERNEL32.DLL (0x7ffc31a00000)
>         KERNELBASE.dll => /cygdrive/c/WINDOWS/System32/KERNELBASE.dll (0x7ffc30090000)
>         cygbz2-1.dll => /usr/bin/cygbz2-1.dll (0x3f6a40000)
>         cygcom_err-2.dll => /usr/bin/cygcom_err-2.dll (0x3ef750000)
>         cyggssapi_krb5-2.dll => /usr/bin/cyggssapi_krb5-2.dll (0x3eceb0000)
>         cygiconv-2.dll => /usr/bin/cygiconv-2.dll (0x3ec980000)
>         cygpcre-1.dll => /usr/bin/cygpcre-1.dll (0x3eb1a0000)
>         cyggcc_s-seh-1.dll => /usr/bin/cyggcc_s-seh-1.dll (0x3ee3a0000)
>         cygstdc++-6.dll => /usr/bin/cygstdc++-6.dll (0x3ea280000)
>         cygz.dll => /cygdrive/u/2.4.0/release/Cygwin-64/bin/cygz.dll (0x3aba30000)
>         cygk5crypto-3.dll => /usr/bin/cygk5crypto-3.dll (0x3ec300000)
>         cygwin1.dll => /cygdrive/u/2.4.0/release/Cygwin-64/bin/cygwin1.dll (0x180040000)
>         ??? => ??? (0xe80000)
>         ??? => ??? (0x1440000)
>         ??? => ??? (0xe80000)
>         cygkrb5-3.dll => /usr/bin/cygkrb5-3.dll (0x3ec170000)
>         cygkrb5support-0.dll => /usr/bin/cygkrb5support-0.dll (0x3ec150000)
>         cygintl-8.dll => /usr/bin/cygintl-8.dll (0x3ec8d0000)
> 
> 2.
>         ntdll.dll => /cygdrive/c/WINDOWS/SYSTEM32/ntdll.dll (0x7ffc339d0000)
>         KERNEL32.DLL => /cygdrive/c/WINDOWS/System32/KERNEL32.DLL (0x7ffc31a00000)
>         KERNELBASE.dll => /cygdrive/c/WINDOWS/System32/KERNELBASE.dll (0x7ffc30090000)
>         cygbz2-1.dll => /usr/bin/cygbz2-1.dll (0x3f6a40000)
>         cygcom_err-2.dll => /usr/bin/cygcom_err-2.dll (0x3ef750000)
>         cyggssapi_krb5-2.dll => /usr/bin/cyggssapi_krb5-2.dll (0x3eceb0000)
>         cygiconv-2.dll => /usr/bin/cygiconv-2.dll (0x3ec980000)
>         cygpcre-1.dll => /usr/bin/cygpcre-1.dll (0x3eb1a0000)
>         cygwin1.dll => /cygdrive/u/2.4.0/release/Cygwin-64/bin/cygwin1.dll (0x180040000)
>         cyggcc_s-seh-1.dll => /usr/bin/cyggcc_s-seh-1.dll (0x3ee3a0000)
>         cygstdc++-6.dll => /usr/bin/cygstdc++-6.dll (0x3ea280000)
>         cygk5crypto-3.dll => /usr/bin/cygk5crypto-3.dll (0x3ec300000)
>         cygkrb5-3.dll => /usr/bin/cygkrb5-3.dll (0x3ec170000)
>         cygz.dll => /cygdrive/u/2.4.0/release/Cygwin-64/bin/cygz.dll (0x3aba30000)
>         cygkrb5support-0.dll => /usr/bin/cygkrb5support-0.dll (0x3ec150000)
>         cygintl-8.dll => /usr/bin/cygintl-8.dll (0x3ec8d0000)

Libraries may be loaded asynchronously as they are accessed, and ldd just dumps
the dll import table once the subprocess is ready to run.
Perhaps these are import entries that ldd should detect and skip or annotate in
some more useful way.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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