Generated trace event code is written to trace/generated-tracers.c. The
'dtrace' backend does not generate C code, instead the dtrace(1) utility
takes a .dtrace file as input and produces a .o file as output.
Therefore, with 'dtrace' we have:
generated-tracers.o <- generated-tracers.dtrace
Without 'dtrace' we have:
generated-tracers.o <- generated-tracers.c
When QEMU is built with ./configure --enable-trace-backend=simple
followed by ./configure --enable-trace-backend=dtrace, the
generated-tracers.c file remains although the 'dtrace' backend does not
use it.
Because the %.o: %.c target is defined before the %.o: %.dtrace target
in rules.mak, we'll actually pull in the stale .c file instead of using
the .dtrace file! The resulting build is a mix of 'dtrace' and 'simple'
trace backends - and it fails loudly.
Commit 0e848f482bce75f4d9cbac9f495fa45e51d08c9a (build: some
simplifications for "trace/Makefile.objs") changed trace/Makefile.objs
so that 'dtrace' and non-'dtrace' builds use generated-tracers.o.
Previously we used generated-tracers-dtrace.o for 'dtrace' builds only
and generated-tracers.o for non-'dtrace' builds only.
This patch is somewhat ugly. It undoes the change from
0e848f482bce75f4d9cbac9f495fa45e51d08c9a so that the 'dtrace' and
non-'dtrace' builds do not conflict with each other.
The result is that 'dtrace' builds no longer fail if stale
generated-tracers.c files are present.
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
Can someone think of a better way to fix this?
Perhaps we've really outgrown in-tree builds and need to switch to a ./build/
directory that can be blown away each time ./configure runs (fingers crossed
you have ccache installed or the build may take some time).
rules.mak | 2 +-
trace/Makefile.objs | 5 +++--
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/rules.mak b/rules.mak
index 6d82c0d..d8b0672 100644
--- a/rules.mak
+++ b/rules.mak
@@ -29,7 +29,7 @@ else
LIBTOOL += $(if $(V),,--quiet)
%.lo: %.c
$(call quiet-command,$(LIBTOOL) --mode=compile --tag=CC $(CC)
$(QEMU_INCLUDES) $(QEMU_CFLAGS) $(QEMU_DGFLAGS) $(CFLAGS) -c -o $@ $<," lt CC
$@")
-%.lo: %.dtrace
+%-dtrace.lo: %.dtrace
$(call quiet-command,$(LIBTOOL) --mode=compile --tag=CC dtrace -o $@ -G
-s $<, " lt GEN $(TARGET_DIR)$@")
LINK = $(call quiet-command,\
diff --git a/trace/Makefile.objs b/trace/Makefile.objs
index 27fe26b..97e280d 100644
--- a/trace/Makefile.objs
+++ b/trace/Makefile.objs
@@ -24,6 +24,7 @@ $(obj)/generated-tracers.c-timestamp:
$(SRC_PATH)/trace-events $(BUILD_DIR)/conf
@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst
%-timestamp,%,$@)
$(obj)/generated-tracers.o: $(obj)/generated-tracers.c
$(obj)/generated-tracers.h
+util-obj-y += generated-tracers.o
endif
@@ -45,7 +46,8 @@ $(obj)/generated-tracers.dtrace-timestamp:
$(SRC_PATH)/trace-events $(BUILD_DIR)
$(obj)/generated-tracers-dtrace.h: $(obj)/generated-tracers.dtrace
$(call quiet-command,dtrace -o $@ -h -s $<, " GEN $@")
-$(obj)/generated-tracers.o: $(obj)/generated-tracers.dtrace
+$(obj)/generated-tracers-dtrace.o: $(obj)/generated-tracers.dtrace
+util-obj-y += generated-tracers-dtrace.o
endif
######################################################################
@@ -55,4 +57,3 @@ util-obj-$(CONFIG_TRACE_DEFAULT) += default.o
util-obj-$(CONFIG_TRACE_SIMPLE) += simple.o
util-obj-$(CONFIG_TRACE_STDERR) += stderr.o
util-obj-y += control.o
-util-obj-y += generated-tracers.o
--
1.8.1
