gasm-sdk/docs/cli.md

CLI Reference

Repository: sourcedock.dev/petrbalvin/gasm-devkit

gasm is a single binary with subcommands. Run gasm --help for an overview, or gasm <command> -h for a command's usage and flags.

Global Flags

Flag	Description
-h, --help	Show help
-V, --version	Print the version

gasm tokens <file>

Print the lexical token stream of FILE: position, token kind, and text, one token per line. FILE may be - to read standard input.

gasm parse <file>

Parse FILE and report syntax errors on stderr. On success, prints how many declarations and TEXT functions the file contains.

gasm fmt [-w] [path...]

Canonicalise the formatting of Plan 9 assembly sources: indentation, operand spacing, per-function mnemonic alignment, and blank-line layout.

Flag	Description
-w	Write result to the source file (default: print to stdout)

With no arguments, or with a directory argument, every .s file below it is reformatted in place and the names of changed files are listed (go fmt style). . and _ directories are skipped.

gasm lint <file...>

Run static checks and print diagnostics as file:line:col: severity: message [code]. Exit status is non-zero when an error-severity diagnostic is found.

Flag	Description
-disable	Comma-separated rule codes to disable

Rules: unknown-instruction, operand-count, undefined-label, duplicate-label, missing-ret, missing-textflag-include, abi-argsize, unreachable-code, register-clobber, funcdata-pcdata.

gasm asm [--format raw|elf|macho|goobj] [-p pkg] [-o out] <file>

Assemble FILE (amd64) to machine code.

Flag	Description
--format	Output format: raw (default), elf, macho, goobj
-p	Package path (required for --format goobj)
-o	Write output to file (default: hex dump to stdout)

gasm verify [flags] <file.s>

Assemble FILE, map it into executable memory, and run dynamic checks.

Flag	Description
--ground-truth	Compare machine code byte-for-byte against go tool asm
--fuzz	Differential fuzz: JIT both gasm and go-tool-asm, compare outputs
-n	Fuzz iterations per function (default: 1000)
--abi	Run ABI-checking calls (sentinel registers + red zone)
--abi-n	Number of ABI check iterations with varied inputs (default: 100)
--profile	List basic-block structure per function
--smoke	Call each NOSPLIT function with zeroed args
--call <func>	Invoke a single function with --buf instead of the sweeps
--buf <spec>	Buffer spec for --call: name:size:pattern[,name:size:pattern]
--repeat <n>	Number of times to repeat a --call invocation (default: 1)

The --fuzz mode runs each function in a subprocess; a partial function (e.g. a decoder that faults on malformed input) is reported as CRASH without killing the parent. Use --call with --buf to invoke partial functions with valid data instead.

The --call mode parses the // func signature, allocates the requested buffers (zero, ones, seq, or a hex blob), builds the ABI0 argument block with buffer pointers/lengths/capacities at the matching parameter offsets, and prints the arg block before and after the call — showing return values and any output written to the buffers.

gasm debug --func <name> [--buf spec] <file.s>

Interactive debugger for JIT-assembled amd64 functions. Requires a compiled binary on $PATH (not go run).

Flag	Description
--func	Function to debug (required)
--buf	Buffer spec: name:size:pattern[,name:size:pattern]

REPL commands:

Command	Description
break <label|addr>	Set a breakpoint
step [n]	Single-step n instructions
continue	Run until next breakpoint or exit
regs	Print general-purpose + YMM/XMM vector registers
x [addr] [len]	Hex-dump memory
labels	List function labels and offsets
quit	Kill the debuggee and exit

gasm diff [--map old=new,...] <file1.s> <file2.s>

Compare the machine code produced by assembling two files. Shows which functions differ and the first few differing bytes. Useful for verifying that two implementations produce identical code, or for tracking encoding changes between Go assembler versions.

Flag	Description
--map	Comma-separated old=new pairs to match functions with different names

Without --map, functions are paired by exact name. With --map, a function named old in the first file is compared against the function named new in the second file (e.g. --map wideCopyAVX2=wideCopyAVX512 pairs AVX2 and AVX-512 variants regardless of suffix).

gasm profile <file.s>

Show the basic-block structure of functions in an assembly file. Lists each function's labels, their offsets, and the block boundaries. This is the static structure; for runtime execution counts, use gasm verify --fuzz which exercises the code paths.

gasm lsp

Run the language server over standard input/output (JSON-RPC 2.0 with Content-Length framing). Point an LSP-capable editor at the binary and associate it with .s files. The target architecture is inferred from the file-name suffix (_amd64.s, _arm64.s, _riscv64.s, _loong64.s).

Provides: completion, hover, document symbols, diagnostics, and semantic-token highlighting.