padlock-macros

Compile-time struct layout assertions for padlock — the lint pass for struct memory layout.

This crate provides two proc-macro attributes that turn layout regressions into compile errors.

#[padlock::assert_no_padding]

Fails to compile if the struct contains any padding bytes:

use padlock_macros::assert_no_padding;

#[assert_no_padding]
struct Connection {
    timeout: f64,   // 8 bytes, align 8
    port:    u16,   // 2 bytes
    active:  bool,  // 1 byte
    tls:     bool,  // 1 byte
    // no padding — passes
}

If you add a field that causes padding, the build fails with a clear message.

#[padlock::assert_size(N)]

Fails to compile if the struct size is not exactly N bytes. Use this to prevent accidental growth or shrinkage:

use padlock_macros::assert_size;

#[assert_size(16)]
struct Connection {
    timeout: f64,
    port:    u16,
    active:  bool,
    tls:     bool,
}

Both macros pass the struct definition through unchanged — they only append a hidden const assertion block. No runtime cost.

Part of padlock

• padlock-cli — CLI (padlock + cargo-padlock binaries)
• padlock-core — IR, analysis passes, findings
• padlock-source — Source analysis (C/C++/Rust/Go)
• padlock-dwarf — Binary analysis (DWARF/PDB)
• padlock-output — Output formatters (terminal/JSON/SARIF/diff)
• padlock-macros — Compile-time layout assertions (this crate)