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Re: [Qemu-devel] [PATCH] build: reinstate generated-tracers-dtrace.o
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] build: reinstate generated-tracers-dtrace.o |
Date: |
Thu, 24 Jan 2013 18:04:41 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
Il 24/01/2013 16:50, Stefan Hajnoczi ha scritto:
> 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 <address@hidden>
> ---
> Can someone think of a better way to fix this?
Doesn't really look ugly. Thanks for fixing this.
Paolo
> 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
>