Detect and document dependency on -ldl on Linux, -lc on BSD for dlopen

Signed-off-by: Mathieu Desnoyers <[email protected]>

README

@@ -67,15 +67,15 @@ USAGE:
       "TRACEPOINT_DEFINE" and include the tracepoint provider.
     - Use "-I." for the compilation unit containing the tracepoint
       provider include (e.g. tp.c).
-    - Link application with "-ldl".
+    - Link application with "-ldl" on Linux, with "-lc" on BSD.
     - If building the provider directly into the application,
       link the application with "-llttng-ust".
     - If building a static library for the provider, link the static
       library with "-lllttng-ust".
     - Include the tracepoint provider header into all C files using
       the provider.
     - Example:
-        tests/hello/  hello.c tp.c ust_tests_hello.h Makefile.example
+        tests/hello/  hello.c tp.c ust_tests_hello.h Makefile.example.*
 
   2) Compile the Tracepoint Provider separately from the application,
      using dynamic linking:
@@ -87,7 +87,7 @@ USAGE:
       files that use the provider.
     - Compile the tracepoint provider with "-I.".
     - Link the tracepoint provider with "-llttng-ust".
-    - Link application with "-ldl".
+    - Link application with "-ldl" on Linux, "-lc" on BSD.
     - Set a LD_PRELOAD environment to preload the tracepoint provider
       shared object before starting the application when tracing is
       needed.

configure.ac

@@ -42,7 +42,23 @@ AC_PROG_MAKE_SET
 LT_INIT
 
 ## Checks for libraries.
-AC_CHECK_LIB([dl], [dlopen])
+AC_CHECK_LIB([dl], [dlopen],
+[
+	have_libdl=yes
+],
+[
+	#libdl not found, check for dlopen in libc.
+	AC_CHECK_LIB([c], [dlopen],
+	[
+		have_libc_dl=yes
+	],
+	[
+		AC_MSG_ERROR([Cannot find dlopen in libdl nor libc. Use [LDFLAGS]=-Ldir to specify their location.])
+	])
+])
+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"])
+
 AC_CHECK_LIB([pthread], [pthread_create])
 
 # Check for libuuid
@@ -59,7 +75,7 @@ AC_CHECK_LIB([uuid], [uuid_generate],
 		have_libc_uuid=yes
 	],
 	[
-		AC_MSG_ERROR([Cannot find libuuid uuid_generate nor libc uuid_create. Use [LDFLAGS]=-Ldir to specify its location.])
+		AC_MSG_ERROR([Cannot find libuuid uuid_generate nor libc uuid_create. Use [LDFLAGS]=-Ldir to specify their location.])
 	])
 ]
 )

doc/examples/easy-ust/Makefile

@@ -16,7 +16,8 @@
 # the "html" target helps for documentation (req. code2html)
 
 CC = gcc
-LIBS = -ldl -llttng-ust
+LIBS = -ldl -llttng-ust		# On Linux
+#LIBS = -lc -llttng-ust		# On BSD
 CFLAGS = -I.
 
 all: sample

doc/examples/gen-tp/Makefile

@@ -16,7 +16,9 @@
 # provider probe.
 
 CC = gcc
-LIBS = -ldl -llttng-ust
+
+LIBS = -ldl -llttng-ust		#On Linux
+#LIBS = -lc -llttng-ust		#On BSD
 
 all: sample
 

liblttng-ust-fork/Makefile.am

@@ -4,6 +4,13 @@ AM_CFLAGS = -fno-strict-aliasing
 lib_LTLIBRARIES = liblttng-ust-fork.la
 liblttng_ust_fork_la_SOURCES = ustfork.c
 liblttng_ust_fork_la_LIBADD = \
-	-ldl \
 	$(top_builddir)/liblttng-ust/liblttng-ust.la
+
+if LTTNG_UST_BUILD_WITH_LIBDL
+liblttng_ust_fork_la_LIBADD += -ldl
+endif
+if LTTNG_UST_BUILD_WITH_LIBC_DL
+liblttng_ust_fork_la_LIBADD += -lc
+endif
+
 libustfork_CFLAGS = -DUST_COMPONENT=liblttng-ust-fork -fno-strict-aliasing

liblttng-ust-libc-wrapper/Makefile.am

@@ -5,9 +5,16 @@ lib_LTLIBRARIES = liblttng-ust-libc-wrapper.la
 liblttng_ust_libc_wrapper_la_SOURCES = \
 	lttng-ust-malloc.c \
 	ust_libc.h
-liblttng_ust_libc_wrapper_la_LIBADD = -ldl \
+liblttng_ust_libc_wrapper_la_LIBADD = \
 	-L$(top_builddir)/liblttng-ust/.libs \
 	-llttng-ust
 
+if LTTNG_UST_BUILD_WITH_LIBDL
+liblttng_ust_libc_wrapper_la_LIBADD += -ldl
+endif
+if LTTNG_UST_BUILD_WITH_LIBC_DL
+liblttng_ust_libc_wrapper_la_LIBADD += -lc
+endif
+
 noinst_SCRIPTS = run
 EXTRA_DIST = run

tests/demo/Makefile.am

@@ -33,5 +33,11 @@ liblttng_ust_provider_ust_tests_demo3_la_LDFLAGS = \
 
 noinst_PROGRAMS = demo
 demo_SOURCES = demo.c ust_tests_demo.h
-# The demo program only depends on libdl.
-demo_LDFLAGS = -ldl
+# The demo program only depends on libdl/libc for dlopen().
+if LTTNG_UST_BUILD_WITH_LIBDL
+demo_LDADD = -ldl
+endif
+if LTTNG_UST_BUILD_WITH_LIBC_DL
+demo_LDADD = -lc
+endif
+

tests/demo/README

@@ -4,7 +4,8 @@ demo-trace shell script preloads the provider shared objects before
 executing the demo. Executing "demo" without the shell wrapper will not
 provide any tracing support. This ensures the demo binary can be
 distributed on distros without depending on having liblttng-ust.so in
-place. Note: the "demo" program must be compiled with "-ldl".
+place. Note: the "demo" program must be compiled with "-ldl" on Linux,
+with "-lc" on BSD.
 
 The simplest command to trace the demo program are:
 lttng create

tests/dlopen/Makefile.am

@@ -6,7 +6,14 @@ libdummy_la_SOURCES = libdummy.c
 libdummy_la_LIBADD = $(top_builddir)/libust/libust.la $(top_builddir)/libust-initializer.o
 libdummy_la_LDFLAGS = -rpath /nowhere
 dlopen_SOURCES = dlopen.c
-dlopen_LDADD = -ldl $(top_builddir)/libust/libust.la $(top_builddir)/libust-initializer.o
+dlopen_LDADD = $(top_builddir)/libust/libust.la $(top_builddir)/libust-initializer.o
+
+if LTTNG_UST_BUILD_WITH_LIBDL
+dlopen_LDADD += -ldl
+endif
+if LTTNG_UST_BUILD_WITH_LIBC_DL
+dlopen_LDADD += -lc
+endif
 
 noinst_SCRIPTS = run
 EXTRA_DIST = run

tests/hello-static-lib/Makefile.am

@@ -8,7 +8,14 @@ liblttng_ust_provider_ust_test_hello_la_LIBADD = \
 
 noinst_PROGRAMS = hello
 hello_SOURCES = hello.c
-hello_LDADD = -ldl liblttng-ust-provider-ust-test-hello.la
+hello_LDADD = liblttng-ust-provider-ust-test-hello.la
+
+if LTTNG_UST_BUILD_WITH_LIBDL
+hello_LDADD += -ldl
+endif
+if LTTNG_UST_BUILD_WITH_LIBC_DL
+hello_LDADD += -lc
+endif
 
 noinst_SCRIPTS = run
 EXTRA_DIST = run

tests/hello.cxx/Makefile.am

@@ -4,5 +4,12 @@ noinst_PROGRAMS = hello
 hello_SOURCES = hello.cpp tp.c ust_tests_hello.h
 hello_LDADD = $(top_builddir)/liblttng-ust/liblttng-ust.la
 
+if LTTNG_UST_BUILD_WITH_LIBDL
+hello_LDADD += -ldl
+endif
+if LTTNG_UST_BUILD_WITH_LIBC_DL
+hello_LDADD += -lc
+endif
+
 noinst_SCRIPTS = run
 EXTRA_DIST = run

tests/hello/Makefile.am

@@ -4,5 +4,12 @@ noinst_PROGRAMS = hello
 hello_SOURCES = hello.c tp.c ust_tests_hello.h
 hello_LDADD = $(top_builddir)/liblttng-ust/liblttng-ust.la
 
+if LTTNG_UST_BUILD_WITH_LIBDL
+hello_LDADD += -ldl
+endif
+if LTTNG_UST_BUILD_WITH_LIBC_DL
+hello_LDADD += -lc
+endif
+
 noinst_SCRIPTS = run
 EXTRA_DIST = run

tests/hello/Makefile.example.bsd

@@ -0,0 +1,8 @@
+# Example makefile for build outside of the LTTng-UST tree.
+
+hello:
+	${CC} -O2 -I. -o hello -lc -llttng-ust hello.c tp.c
+
+.PHONY: clean
+clean:
+	rm -f hello