golang/go · error

-asan: the version of $(go env CC) could not be parsed

Error message

-asan: the version of $(go env CC) could not be parsed

What it means

When -asan is requested, the go command calls compilerVersion() which runs `$(go env CC) --version`, then (for gcc) `CC -v`, parsing `gcc version N.M` or `clang version N.M`. If running the compiler fails, or the matched version digits cannot be parsed as integers, compilerVersion returns an error and this wraps it. The build aborts because the Asan support requirement cannot be verified without a known compiler version.

Source

Thrown at src/cmd/go/internal/work/init.go:439

				return err
			}
			if compiler.minor, err = strconv.Atoi(string(match[2])); err != nil {
				return err
			}
			return nil
		}()
	})
	return compiler.version, compiler.err
}

// compilerRequiredAsanVersion is a copy of the function defined in
// cmd/cgo/internal/testsanitizers/cc_test.go
// compilerRequiredAsanVersion reports whether the compiler is the version
// required by Asan.
func compilerRequiredAsanVersion() error {
	compiler, err := compilerVersion()
	if err != nil {
		return fmt.Errorf("-asan: the version of $(go env CC) could not be parsed")
	}

	switch compiler.name {
	case "gcc":
		if runtime.GOARCH == "ppc64le" && compiler.major < 9 {
			return fmt.Errorf("-asan is not supported with %s compiler %d.%d\n", compiler.name, compiler.major, compiler.minor)
		}
		if compiler.major < 7 {
			return fmt.Errorf("-asan is not supported with %s compiler %d.%d\n", compiler.name, compiler.major, compiler.minor)
		}
	case "clang":
		if compiler.major < 9 {
			return fmt.Errorf("-asan is not supported with %s compiler %d.%d\n", compiler.name, compiler.major, compiler.minor)
		}
	default:
		return fmt.Errorf("-asan: C compiler is not gcc or clang")
	}
	return nil

View on GitHub (pinned to b6b368adc5)

Solutions

1. Ensure `go env CC` points to real gcc or clang: run `$(go env CC) --version` and check the output
2. Upgrade the C compiler to an Asan-capable version (gcc >= 7, clang >= 9)
3. Drop -asan if AddressSanitizer is not required

Example fix

// before (unparseable / missing compiler)
CC=my-wrapper go build -asan ./...
// after
CC=gcc go build -asan ./...

// Verify CC is real gcc/clang with parseable version before -asan
cc := os.Getenv("CC")
if cc == "" { cc = "cc" }
out, err := exec.Command(cc, "--version").Output()
if err != nil || (!bytes.HasPrefix(out, []byte("gcc")) && !bytes.Contains(out, []byte("clang version"))) {
    return fmt.Errorf("CC must be gcc or clang with parseable --version for -asan")
}

When it happens

Trigger: Fires in compilerRequiredAsanVersion when compilerVersion() returns a non-nil error - i.e. CC --version or CC -v failed to execute, or strconv.Atoi on the matched major/minor failed.

Common situations: $CC unset or pointing to a non-existent/wrapper compiler whose --version output is non-standard or fails, a compiler that exits non-zero on --version, or a version string whose digits are not pure integers.

Related errors

• -asan is not supported with %s compiler %d.%d\n
• -asan: C compiler is not gcc or clang
• parsing $CGO_%s_ALLOW: %v
• parsing $CGO_%s_DISALLOW: %v
• unclosed quote

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/c37f055f6ae0a154. Report an issue: GitHub.