[Buildroot] [git commit] Makefile: test if dot exists before using it in graph-depends

[Peter Korsgaard]

commit: http://git.buildroot.net/buildroot/commit/?id=664f2707246a53669f91a83d9cc094c26e3848f3
branch: http://git.buildroot.net/buildroot/commit/?id=refs/heads/master

The 'graph-depends' logic uses the 'dot' program from Graphviz to draw
the dependency graph, but it doesn't check its existence before
starting the generation of the graph, which can lead to user confusion
as reported in:

 http://lists.busybox.net/pipermail/buildroot/2014-June/099278.html

With this commit, we first test if the 'dot' program is available, and
if it's not, we error out with a clear error message:

$ make graph-depends
ERROR: The 'dot' program from Graphviz is needed for graph-depends
make: *** [graph-depends] Error 1

[Peter: send error message to stderr instead]
Reported-by: Dallas Clement <dallas.a.clement at gmail.com>
Cc: Dallas Clement <dallas.a.clement at gmail.com>
Cc: Yann E. MORIN <yann.morin.1998 at free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 Makefile |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/Makefile b/Makefile
index 5501068..14fca2b 100644
--- a/Makefile
+++ b/Makefile
@@ -674,6 +674,8 @@ graph-build: $(O)/build/build-time.log
 				   $(if $(BR2_GRAPH_ALT),--alternate-colors)$(sep))
 
 graph-depends:
+	@dot -? >/dev/null 2>&1 || \
+		(echo "ERROR: The 'dot' program from Graphviz is needed for graph-depends" >&2; exit 1)
 	@$(INSTALL) -d $(O)/graphs
 	@cd "$(CONFIG_DIR)"; \
 	$(TOPDIR)/support/scripts/graph-depends $(BR2_GRAPH_DEPS_OPTS) \