doc

Overview of xgo

xgo is a wrapper around go.

All magic is behind the go's -toolexec flag.

Run go help build, and you will find this flag:

-toolexec 'cmd args'
        a program to use to invoke toolchain programs like vet and asm.
        For example, instead of running asm, the go command will run
        'cmd args /path/to/asm <arguments for asm>'.
        The TOOLEXEC_IMPORTPATH environment variable will be set,
        matching 'go list -f {{.ImportPath}}' for the package being built.

When you run xgo build ./my/example, it does the following things:

1. find the GOROOT,
2. copy the GOROOT into ~/.xgo/go-instruments/GOROOT to prepare for instrumenting,
3. apply patch to ~/.xgo/go-instruments/GOROOT, both for compiler and runtime,
4. build the instrumented compiler,
5. invoke go build with extra flag: go build -toolexec exec_tool ./my/example,
6. the exec_tool then forward all compile command to the instrumented compiler
7. once all compilation finished, go invoke link to generate the executable, and you get a instrumented binary!