On 2/15/20 10:22 PM, Eric Blake wrote:
At least the VDDK plugin needs a way to load .so files with a custom
directory prepended. Asking the user to set LD_LIBRARY_PATH is too
strong (that would leak into the child process created by --run, and
makes the user think about issues that we'd rather cover
automatically). But overriding dlopen() to make it easier to prepend
a directory name under our control requires either a separate
namespace via dlmopen() (which itself is annoying - it messes up gdb
debugging), or that the override occur prior to any other library that
also depends on -ldl. Which means that if we are going to provide
this functionality, we have to do so from nbdkit proper.
Note that properly injecting a dlopen shim for all subsequent shared
library loads requires that the override itself be in a shared
library. Thus, nbdkit has to pull it in via a shared library link,
rather than merely a .o file, and we now have to install something in
pkglibdir. What's more, now that we link against a shared library
instead of just libtool convenience libraries, libtool now creates a
wrapper app named lt-nbdkit so that it can run an in-tree build that
still locates the uninstalled shared library; this affects some
expected output in tests.
The wrapper script also needs a tweak thanks to libtool's behavior; I'll
have to squash this in:
diff --git i/wrapper.c w/wrapper.c
index 6aef81a1..b0b9c158 100644
--- i/wrapper.c
+++ w/wrapper.c
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2017-2019 Red Hat Inc.
+ * Copyright (C) 2017-2020 Red Hat Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
@@ -148,6 +148,8 @@ main (int argc, char *argv[])
*/
s = getenv ("NBDKIT_VALGRIND");
if (s && strcmp (s, "1") == 0) {
+ passthru ("libtool");
+ passthru ("execute");
passthru (VALGRIND);
passthru ("--vgdb=no");
passthru ("--leak-check=full");
@@ -163,6 +165,8 @@ main (int argc, char *argv[])
else {
s = getenv ("NBDKIT_GDB");
if (s && strcmp (s, "1") == 0) {
+ passthru ("libtool");
+ passthru ("execute");
passthru ("gdb");
passthru ("--args");
}
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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