When a string variable already had a source-level default value, the -ldflags
"-X" flag was silently ignored and the variable remained the default value
at runtime.
Fix by stripping the InitOrder entry for each -X variable before
LoadSSA() is called. With no entry in InitOrder, go/ssa emits no init
store, so the global stays zero-valued in the IR. makeGlobalsModule
still injects the actual -X values at final link time.
The -X values remain out of the per-package build cache with only the
variable names appearing in the cache key.
Signed-off-by: deadprogram <ron@hybridgroup.com>
This commit implements replacing some global variables with a different
value, if the global variable has no initializer. For example, if you
have:
package main
var version string
you can replace the value with -ldflags="-X main.version=0.2".
Right now it only works for uninitialized globals. The Go tooling also
supports initialized globals (var version = "<undefined>") but that is a
bit hard to combine with how initialized globals are currently
implemented.
The current implementation still allows caching package IR files while
making sure the values don't end up in the build cache. This means
compiling a program multiple times with different values will use the
cached package each time, inserting the string value only late in the
build process.
Fixes#1045
deadprogram
Ayke van Laethem