From 44316d0214425f5ae0d8af07099caae3e95ac890 Mon Sep 17 00:00:00 2001
From: Romain Naour <romain.naour@openwide.fr>
Date: Tue, 8 Apr 2014 22:15:27 +0200
Subject: [PATCH 1/1] Fix: disable liblttng-ust-dl if dlinfo is not available
 in C library

According to uClibc commit [1], dlinfo is not available in recent uClibc (>0.9.33),
but is available in older version of uClibc (<=0.9.33) whith a different prototype
than dlinfo() in glibc.

To be able to use LTTng UST with uClibc, we need to disable the Dynamic Linker
Tracing functionality [2].

A specific test on dlinfo() prototype is performed to enable or disable this
functionality.

[1] http://git.uclibc.org/uClibc/commit/?id=f3c9dc499c5c787ddd8c4320f2d44d2ae6e40c22
[2] http://lists.lttng.org/pipermail/lttng-dev/2014-February/022423.html

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
---
 Makefile.am  |  5 ++++-
 configure.ac | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/Makefile.am b/Makefile.am
index b79d2dd..c907ff1 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -4,11 +4,14 @@ SUBDIRS = . include snprintf libringbuffer liblttng-ust-comm \
 		liblttng-ust \
 		liblttng-ust-ctl \
 		liblttng-ust-fork \
-		liblttng-ust-dl \
 		liblttng-ust-libc-wrapper \
 		liblttng-ust-cyg-profile \
 		tools
 
+if HAVE_DLINFO
+SUBDIRS += liblttng-ust-dl
+endif
+
 if BUILD_JNI_INTERFACE
 SUBDIRS += liblttng-ust-java liblttng-ust-jul
 endif
diff --git a/configure.ac b/configure.ac
index b04d4e3..f4b499b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -119,8 +119,26 @@ AC_CHECK_LIB([dl], [dlopen],
 		AC_MSG_ERROR([Cannot find dlopen in libdl nor libc. Use [LDFLAGS]=-Ldir to specify their location.])
 	])
 ])
+AS_IF([test "$x$have_libdl" = "yes" || test "x$have_libc_dl" = "xyes"],
+	[AC_MSG_CHECKING([for dlinfo()])
+		# Ensure the check is covered by the LIBS variable
+		LIBS="$LIBS -ldl"
+		AC_LINK_IFELSE(
+			[AC_LANG_PROGRAM([[#define _GNU_SOURCE /* Required on Linux to get GNU extensions */
+							#include <dlfcn.h>]],
+				[[dlinfo(0, 0, 0);]])],
+			[AC_MSG_RESULT([yes])
+				dlinfo_ok=yes;
+			],
+			[AC_MSG_RESULT([no])
+				AC_MSG_WARN([dlinfo() is not available, the Dynamic Linker Tracing functionality is disabled.])
+				dlinfo_ok=no;
+			])
+	],
+	[dlinfo_ok=no])
 AM_CONDITIONAL([LTTNG_UST_BUILD_WITH_LIBDL], [test "x$have_libdl" = "xyes"])
 AM_CONDITIONAL([LTTNG_UST_BUILD_WITH_LIBC_DL], [test "x$have_libc_dl" = "xyes"])
+AM_CONDITIONAL([HAVE_DLINFO], [test "dlinfo_ok" = "yes"])
 
 AC_CHECK_LIB([pthread], [pthread_create])
 
-- 
1.9.0