[PATCH] perf/jvmti: improve error message in Makefile

[Stephane Eranian]

This patch improves the error message given by jvmti Makefile
when the alternatives command cannot be found. It now suggests
the user locates the root of their Java installation and pass it
with JDIR=

Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx>
---
 tools/perf/jvmti/Makefile | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/tools/perf/jvmti/Makefile b/tools/perf/jvmti/Makefile
index 0277a64b391b..5ce61a1bda9c 100644
--- a/tools/perf/jvmti/Makefile
+++ b/tools/perf/jvmti/Makefile
@@ -35,12 +35,21 @@ SOLIBEXT=so
 
 # The following works at least on fedora 23, you may need the next
 # line for other distros.
-ifeq (,$(wildcard /usr/sbin/update-java-alternatives))
-JDIR=$(shell alternatives --display java | tail -1 | cut -d' ' -f 5 | sed 's%/jre/bin/java.%%g')
-else
+ifneq (,$(wildcard /usr/sbin/update-java-alternatives))
 JDIR=$(shell /usr/sbin/update-java-alternatives -l | head -1 | cut -d ' ' -f 3)
+else
+  ifneq (,$(wildcard /usr/sbin/alternatives))
+    JDIR=$(shell alternatives --display java | tail -1 | cut -d' ' -f 5 | sed 's%/jre/bin/java.%%g')
+  endif
 endif
-
+ifndef JDIR
+$(error Could not find alternatives command, you need to set JDIR= to point to the root of your Java directory)
+else
+  ifeq (,$(wildcard $(JDIR)/include/jvmti.h))
+  $(error the openjdk development package appears to me missing, install and try again)
+  endif
+endif
+$(info Using Java from $(JDIR))
 # -lrt required in 32-bit mode for clock_gettime()
 LIBS=-lelf -lrt
 INCDIR=-I $(JDIR)/include -I $(JDIR)/include/linux
-- 
1.9.1