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43f4d9 |
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43f4d9 |
Add $APR_DEEPBIND to enable use of RTLD_DEEPBIND in apr_dso_open().
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--- apr-1.4.8/dso/unix/dso.c.deepbind
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+++ apr-1.4.8/dso/unix/dso.c
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@@ -38,6 +38,8 @@
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#define DYLD_LIBRARY_HANDLE (void *)-1
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#endif
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ec8672 |
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+static int use_deepbind; /* 0 = unset, 1 = use DEEPBIND, -1, don't use DEEPBIND */
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+
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APR_DECLARE(apr_status_t) apr_os_dso_handle_put(apr_dso_handle_t **aprdso,
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apr_os_dso_handle_t osdso,
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apr_pool_t *pool)
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@@ -125,6 +127,12 @@
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ec8672 |
#else
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int flags = RTLD_NOW | RTLD_GLOBAL;
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void *os_handle;
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+
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+ if (use_deepbind == 0)
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+ use_deepbind = getenv("APR_DEEPBIND") != NULL ? 1 : -1;
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+ if (use_deepbind == 1)
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+ flags |= RTLD_DEEPBIND;
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+
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ec8672 |
#ifdef _AIX
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if (strchr(path + 1, '(') && path[strlen(path) - 1] == ')')
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{
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43f4d9 |
--- apr-1.7.0/README.deepbind.deepbind
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43f4d9 |
+++ apr-1.7.0/README.deepbind
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@@ -0,0 +1,30 @@
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+This distribution of APR contains a modification of the behaviour of
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+the apr_dso_open() function which allows users enable the
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+"RTLD_DEEPBIND" flag when dlopen() is called.
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+
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+If the "APR_DEEPBIND" environment variable is set at runtime, the
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+RTLD_DEEPBIND flag is always added to the flags passed to dlopen().
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+
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+With normal use of dlopen(), dynamically loaded objects will use
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+global symbols in preference to any symbols defined within the object.
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+Using RTLD_DEEPBIND reverses this binding order. See the dlopen(3)
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+man page for more information.
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+
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+This can be useful with Apache httpd, where two different modules are
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+loaded like:
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+
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+1. mod_foo.so uses library "libfoo.so"
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+ libfoo.so defines a function "SomeSym"
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+2. mod_bar.so uses library "libbar.so"
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+ libbar.so defines a different "SomeSym" function
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+
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+By default, mod_bar or mod_foo would use the "SomeSym" definition from
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+the "wrong" library depending on the load order. If RTLD_DEEPBIND is
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+used, the "SomeSym" definition will always be mapped to the definition
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+from the corresponding dependent library. This can avoid symbol
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+conflicts.
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43f4d9 |
+
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+There are some risks with using RTLD_DEEPBIND, in particular potential
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43f4d9 |
+issues with modules written in C++. It is not recommended to enable
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43f4d9 |
+$APR_DEEPBIND unless it solves a specific problem and after thorough
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43f4d9 |
+testing of the configuration.
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