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From: "mail at milianw dot de" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug dynamic-link/28248] is there a way to LD_PRELOAD library before
 other dynamic libraries?
Date: Thu, 09 Sep 2021 08:54:20 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28248

--- Comment #5 from Milian Wolff <mail at milianw dot de> ---
I just tried the linker flag with the example given above, but sadly it doe=
sn't
help as only the `calling init` is changed, but `calling fini` isn't - this=
 was
probably what you had in mind when you raised the potential issue about
constructor/destructor order.

```
$ gcc -shared -fPIC -o preload_dump.so preload_dump.c
LD_DEBUG=3Dfiles LD_PRELOAD=3D$PWD/preload_dump.so bash --version |& grep -i
calling
      7413:     calling init: /lib64/ld-linux-x86-64.so.2
      7413:     calling init: /usr/lib/libc.so.6
      7413:     calling init: /usr/lib/libncursesw.so.6
      7413:     calling init: /usr/lib/libdl.so.2
      7413:     calling init: /usr/lib/libreadline.so.8
      7413:     calling init: /tmp/preload_dump.so
      7413:     calling fini: bash [0]
      7413:     calling fini: /tmp/preload_dump.so [0]
      7413:     calling fini: /usr/lib/libreadline.so.8 [0]
      7413:     calling fini: /usr/lib/libdl.so.2 [0]
      7413:     calling fini: /usr/lib/libncursesw.so.6 [0]

$ gcc -shared -fPIC -Wl,-z,initfirst -o preload_dump.so preload_dump.c
$ LD_DEBUG=3Dfiles LD_PRELOAD=3D$PWD/preload_dump.so bash --version |& grep=
 -i
calling
      7373:     calling init: /tmp/preload_dump.so
      7373:     calling init: /lib64/ld-linux-x86-64.so.2
      7373:     calling init: /usr/lib/libc.so.6
      7373:     calling init: /usr/lib/libncursesw.so.6
      7373:     calling init: /usr/lib/libdl.so.2
      7373:     calling init: /usr/lib/libreadline.so.8
      7373:     calling fini: bash [0]
      7373:     calling fini: /tmp/preload_dump.so [0]
      7373:     calling fini: /usr/lib/libreadline.so.8 [0]
      7373:     calling fini: /usr/lib/libdl.so.2 [0]
      7373:     calling fini: /usr/lib/libncursesw.so.6 [0]
```

Too bad! That would seem to indicate that I'm out of luck here and must stop
calling `__libc_freeres` - or does someone have an alternative suggestion I
could employ?

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