In 90fa325da7, the obfuscation logic was changed to use hashes for
exported names, but incremental names starting at just one letter for
unexported names. Presumably, this was done for the sake of binary size.
I argue that this is not a good idea for the default mode for a number
of reasons:
1) It makes reversing of stack traces nearly impossible for unexported
names, since replacing an obfuscated name "c" with "originalName"
would trigger too many false positives by matching single characters.
2) Exported and unexported names aren't different. We need to know how
names were obfuscated at a later time in both cases, thanks to use
cases like -ldflags=-X. Using short names for one but not the other
doesn't make a lot of sense, and makes the logic inconsistent.
3) Shaving off three bytes for unexported names doesn't seem like a huge
deal for the default mode, when we already have -tiny to optimize for
size.
This saves us a bit of work, but most importantly, simplifies the
obfuscation state as we no longer need to carry privateNameMap between
the compile and link stages.
name old time/op new time/op delta
Build-8 153ms ± 2% 150ms ± 2% ~ (p=0.065 n=6+6)
name old bin-B new bin-B delta
Build-8 7.09M ± 0% 7.08M ± 0% -0.24% (p=0.002 n=6+6)
name old sys-time/op new sys-time/op delta
Build-8 296ms ± 5% 277ms ± 6% -6.50% (p=0.026 n=6+6)
name old user-time/op new user-time/op delta
Build-8 562ms ± 1% 558ms ± 3% ~ (p=0.329 n=5+6)
Note that I do not oppose using short names for both exported and
unexported names in the future for -tiny, since reversing of stack
traces will by design not work there. The code can be resurrected from
the git history if we want to improve -tiny that way in the future, as
we'd need to store state in header files again.
Another major cleanup we can do here is to no longer use the
garbledImports map. From a look at obfuscateImports, we hash a package's
import path with its action ID, much like exported names, so we can
simply re-do that hashing for the linker's -X flag.
garbledImports does have some logic to handle duplicate package names,
but it's worth noting that should not affect package paths, as they are
always unique. That area of code could probably do with some
simplification in the future, too.
While at it, make hashWith panic if either parameter is empty.
obfuscateImports was hashing the main package path without a salt due to
a bug, so we want to catch those in the future.
Finally, make some tiny spacing and typo tweaks to the README.
main.go includes a lengthy comment that documents this edge case, why it
happened, and how we are fixing it. To summarize, we should no longer
error with a build error in those cases. Read the comment for details.
A few other minor changes were done to allow writing this patch.
First, the actionID and contentID funcs were renamed, since they started
to collide with variable names.
Second, the logging has been improved a bit, which allowed me to debug
the issue.
Third, the "cache" global shared by all garble sub-processes now
includes the necessary parameters to run "go list -toolexec", including
the path to garble and the build flags being used.
Thanks to lu4p for writing a test case, which also applied gofmt to that
testdata Go file.
Fixes#180.
Closes#181, since it includes its test case.
Previously garble heavily used env vars to share data between processes.
This also makes it easy to share complex data between processes.
The complexity of main.go is considerably reduced.
The previous globals worked, but were unnecessarily complex. For
example, we passed the fromPath variable around, but it's really a
static global, since we only compile or link a single package in each Go
process. Use such global variables instead of passing them around, which
currently include the package's import path, its build ID, and its
import config path.
Also split all the hashing and build ID code into hash.go, since that's
a relatively well contained 200 lines of code that doesn't need to make
main.go any bigger. We also split the code to alter Go's own version to
a separate function, so that it can be moved out of main.go as well.
Daniel Martí
lu4p