Understanding the Go Build Process

We will discuss Go’s tooling philosophy, understand the Go build process, and examine the go build command.

Overview

Go prides itself on its tooling. Unlike many programming languages where the tooling is an afterthought or even left for the community, Go considers the tooling a big part of what the language offers. Modern Go builds packages and manages dependencies using modules. The old school GOPATH is still supported for backwards compatibility, but unless you maintain a legacy system and can’t move forward, you should solely focus on Go modules.

The primary tool is the go build command that lets us also embed information when linking the program. go build invokes the linker by default.

Multi-git can take advantage of this capability and print useful versioning information.

Understanding the Go build process

Go builds packages. These packages can be executables, static packages, or dynamic packages. When you create an executable by building a program with a main package the resulting binary may still depend on a dynamically linked library. To make an executable truly static you need to provide some flags.

Go can also integrate tightly with C using a special import statement and the CGO tool.

All these nuances of the build process, and many more, are controlled by various build flags.

The go build command

Here is the signature of go build:

go build [-o output] [-i] [build flags] [packages]

We will focus on the build flags:

	-a
		force rebuilding of packages that are already up-to-date.
	-n
		print the commands but do not run them.
	-p n
		the number of programs, such as build commands or
		test binaries, that can be run in parallel.
		The default is the number of CPUs available.
	-race
		enable data race detection.
		Supported only on linux/amd64, freebsd/amd64, darwin/amd64, windows/amd64,
		linux/ppc64le and linux/arm64 (only for 48-bit VMA).
	-msan
		enable interoperation with memory sanitizer.
		Supported only on linux/amd64, linux/arm64
		and only with Clang/LLVM as the host C compiler.
		On linux/arm64, pie build mode will be used.
	-v
		print the names of packages as they are compiled.
	-work
		print the name of the temporary work directory and
		do not delete it when exiting.
	-x
		print the commands.

	-asmflags '[pattern=]arg list'
		arguments to pass on each go tool asm invocation.
	-buildmode mode
		build mode to use. See 'go help buildmode' for more.
	-compiler name
		name of compiler to use, as in runtime.Compiler (gccgo or gc).
	-gccgoflags '[pattern=]arg list'
		arguments to pass on each gccgo compiler/linker invocation.
	-gcflags '[pattern=]arg list'
		arguments to pass on each go tool compile invocation.
	-installsuffix suffix
		a suffix to use in the name of the package installation directory,
		in order to keep output separate from default builds.
		If using the -race flag, the install suffix is automatically set to race
		or, if set explicitly, has _race appended to it. Likewise for the -msan
		flag. Using a -buildmode option that requires non-default compile flags
		has a similar effect.
	-ldflags '[pattern=]arg list'
		arguments to pass on each go tool link invocation.
	-linkshared
		build code that will be linked against shared libraries previously
		created with -buildmode=shared.
	-mod mode
		module download mode to use: readonly, vendor, or mod.
		See 'go help modules' for more.
	-modcacherw
		leave newly-created directories in the module cache read-write
		instead of making them read-only.
	-modfile file
		in module aware mode, read (and possibly write) an alternate go.mod
		file instead of the one in the module root directory. A file named
		"go.mod" must still be present in order to determine the module root
		directory, but it is not accessed. When -modfile is specified, an
		alternate go.sum file is also used: its path is derived from the
		-modfile flag by trimming the ".mod" extension and appending ".sum".
	-pkgdir dir
		install and load all packages from dir instead of the usual locations.
		For example, when building with a non-standard configuration,
		use -pkgdir to keep generated packages in a separate location.
	-tags tag,list
		a comma-separated list of build tags to consider satisfied during the
		build. For more information about build tags, see the description of
		build constraints in the documentation for the go/build package.
		(Earlier versions of Go used a space-separated list, and that form
		is deprecated but still recognized.)
	-trimpath
		remove all file system paths from the resulting executable.
		Instead of absolute file system paths, the recorded file names
		will begin with either "go" (for the standard library),
		or a module path@version (when using modules),
		or a plain import path (when using GOPATH).
	-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>'.

There are many flags, but for the purpose of this course, we will consider the linker flags specified via -ldflags.

As mentioned earlier the go build command also runs the linker tool when building an executable.

In the next lesson, we will look at building packages with Go.