Compiler & Linker Flags — Hands-on Tasks¶

Work through these in order. Go 1.21+.

Task 1: Strip a binary¶

Build a simple "hello world" program twice: once with default flags, once with -ldflags='-s -w'.

Acceptance criteria - [ ] Both binaries produce the same output. - [ ] Stripped version is ≥10% smaller. - [ ] You note the file sizes.

Task 2: Inject a version¶

Add var version = "dev" to your main package. Build with -ldflags="-X main.version=v1.0.0".

Acceptance criteria - [ ] Running the program prints "v1.0.0". - [ ] Running without the flag prints "dev". - [ ] You try injecting into a const and observe that it doesn't work.

Task 3: Buildinfo package¶

Create pkg/buildinfo/buildinfo.go with Version, GitCommit, BuildTime. Inject all three via -ldflags.

Acceptance criteria - [ ] All three values are settable from the command line. - [ ] Your main package prints them. - [ ] You build with git rev-parse --short HEAD for GitCommit.

Task 4: `-trimpath` effect¶

Build a binary that panics. Compare stack traces with and without -trimpath.

Acceptance criteria - [ ] Without: paths like /Users/you/project/main.go. - [ ] With: paths like example.com/myproj/main.go. - [ ] You note one benefit and one drawback.

Task 5: Debug build¶

Build with -gcflags='all=-N -l' and run under delve exec.

Acceptance criteria - [ ] delve can step into your code at the source level. - [ ] You set a breakpoint in main and inspect a variable. - [ ] You also try without -N -l and see the difference (optimized variables may not be visible).

Task 6: See escape decisions¶

Build with -gcflags='-m' and identify three escaped values in your program.

Acceptance criteria - [ ] You list each escape and the reason given by the compiler. - [ ] You modify one to avoid escape and confirm with -m.

Task 7: Cross-compile¶

Build for linux/amd64, linux/arm64, darwin/arm64, windows/amd64.

Acceptance criteria - [ ] All four produce binaries. - [ ] You confirm the platform with file ./binary (on Linux) or by other means. - [ ] You list the binary sizes.

Task 8: Race-detector test¶

Write code with an obvious data race. Run go test -race ./... and observe.

Acceptance criteria - [ ] Test passes without -race. - [ ] Test fails with -race, showing the race details. - [ ] You fix the race with a sync.Mutex and re-run.

Task 9: PGO workflow¶

Capture a CPU profile from a small benchmark and rebuild with PGO.

Acceptance criteria - [ ] go test -cpuprofile=cpu.pgo -bench=. ./pkg produces a profile. - [ ] Place cpu.pgo as cmd/app/default.pgo. - [ ] go build -pgo=auto ./cmd/app succeeds. - [ ] Bench shows some difference (may be small for trivial programs).

Task 10: Build info inspection¶

Run go version -m on your binary.

Acceptance criteria - [ ] You see the Go version, module info, tags, and flags. - [ ] You verify -X injections show up in the embedded metadata. - [ ] You compare two binaries built with different -tags sets.

Task 11: Reproducible build¶

Build the same source twice with:

go build -trimpath -buildvcs=false \
  -ldflags="-buildid='' -s -w" \
  -o app .

Acceptance criteria - [ ] sha256sum app produces the same hash both times. - [ ] You change a single line, rebuild, and confirm the hash changes.

Task 12: Static binary¶

Build a fully static binary.

Acceptance criteria - [ ] CGO_ENABLED=0 go build -ldflags='-s -w' . on Linux. - [ ] file ./binary reports "statically linked" or "no dynamic dependencies". - [ ] Binary works in a scratch Docker container.

Task 13: `-x -work` inspection¶

Build with -x -work and explore the work directory.

Acceptance criteria - [ ] You list the directories and files in $WORK. - [ ] You identify one compile command and one link command. - [ ] You explain in one paragraph what go build actually does.

Stretch — Task 14: Makefile bundle¶

Write a Makefile with build, release, debug, cross, clean targets.

Acceptance criteria - [ ] make build is fast and produces a normal binary. - [ ] make release produces stripped, version-injected, reproducible binary. - [ ] make debug produces a delve-friendly binary. - [ ] make cross produces binaries for at least 3 (GOOS, GOARCH) pairs. - [ ] You commit the Makefile to the repo.

Submission¶

Code + brief notes per task. The end state: a clean build pipeline you can replicate across projects.