Comment #4 on issue 4171 by [email protected]: make sometimes "misses"
dependencies on natives and will not rebuild the external startup blobs
https://code.google.com/p/v8/issues/detail?id=4171
If, instead of the 2nd make, you run:
$ make BUILDTYPE=Release -n -d
... you will get a load of output, containing something like this:
Finished prerequisites of target file `Release/natives_blob.bin'.
Prerequisite `../tools/concatenate-files.py' is older than target
`Release/natives_blob.bin'.
Prerequisite `Release/obj/gen/libraries.bin' is older than target
`Release/natives_blob.bin'.
Prerequisite `Release/obj/gen/libraries-experimental.bin' is older than
target `Release/natives_blob.bin'.
Prerequisite `Release/obj/gen/libraries-extras.bin' is older than
target `Release/natives_blob.bin'.
Prerequisite `FORCE_DO_CMD' of target `Release/natives_blob.bin' does
not exist.
Prerequisite `Release/obj.target/tools/gyp/js2c.stamp' is order-only
for target `Release/natives_blob.bin'.
Must remake target `Release/natives_blob.bin'.
Need a job token; we don't have children
Successfully remade target file `Release/natives_blob.bin'.
This nicely highlights all the bizarreness of gyp-generated makefiles:
- Note that it decides "Must remake target Release/natives_blob.bin"
- Note it says "Successfully remade target file Release/natives_blob.bin"
- Note that it didn't actually do anything in the middle.
- That's the result of FORCE_DO_CMD + $(call do_cmd,...).
- The gyp generated makefile *always* runs commands. That's for
FORCE_DO_CMD does.
- Then, the do_cmd macro figures out whether it had to rebuilt in the
first place.
- This, apparently, works as intended.
- The interesting part is that it claims all prerequisites are older.
- This includes Release/obj/gen/libraries-experimental.bin which was, in
fact, changed in the CL.
Earlier in the same log, you will find:
Finished prerequisites of target file
`Release/obj/gen/libraries-experimental.bin'.
Prerequisite
`_mnt_vogelheim_chrome_v8_v8_tools_gyp_v8_gyp_js2c_target_js2c_experimental.intermediate'
of target `Release/obj/gen/libraries-experimental.bin' does not exist.
No commands for `Release/obj/gen/libraries-experimental.bin' and no
prerequisites actually changed.
No need to remake target `Release/obj/gen/libraries-experimental.bin'.
- Note the line: "No commands for .../libraries-experimental.bin and no
prerequisites actually changes."
- Here, make decided that libraries-experimental.bin did not change, even
though it did.
What this means is that make tried making the inputs, but did not see the
inputs being changed/generated DURING EXECUTION OF THE RESPECTIVE RULES.
Now, examine out/tools/gyp/js2c.target.mk:
$(obj)/gen/libraries.cc $(obj)/gen/libraries.bin:
_mnt_vogelheim_chrome_v8_v8_tools_gyp_v8_gyp_js2c_target_js2c.intermediate
.INTERMEDIATE:
_mnt_vogelheim_chrome_v8_v8_tools_gyp_v8_gyp_js2c_target_js2c.intermediate
_mnt_vogelheim_chrome_v8_v8_tools_gyp_v8_gyp_js2c_target_js2c.intermediate:
$(srcdir)/tools/js2c.py [.. all the args ..] FORCE_DO_CMD
$(call
do_cmd,_mnt_vogelheim_chrome_v8_v8_tools_gyp_v8_gyp_js2c_target_js2c)
These rules use an intermediate rule, to properly handle a rule with
multiple outputs. Note that the nominal targets of those rules are not, in
fact, generated or modified in those rules. I think this is what causes the
behaviour above.
Adding a 'touch' to each of those rules should solve the problem.
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