Compare metadata produced by successive invocations of rustc

metadiff.sh

#!/bin/bash

set -e

if [ -z "$RUSTC" ]; then
    RUSTC=rustc
fi

crate="$1"

if [ -z "$crate" ]; then
    echo "usage: metadiff.sh <crate-name>"
    echo
    echo "Compiles the given crate (.rs file) twice, comparing the produced metadata."
    exit 1
fi

function compile {
    output="$1"
    echo "Compiling $crate to $output ..."

    $RUSTC --crate-type=rlib "$crate" -o "$output"
}

function extract {
    rlib="$1"
    output="$2"

    echo "Extracting metadata from $rlib to $output ..."

    ar p "$rlib" rust.metadata.bin > "$output"
}

$RUSTC -V

compile "first.rlib" &
compile "second.rlib" &
wait %% %-

extract "first.rlib" "metadata.0"
extract "second.rlib" "metadata.1"

echo "Diffing metadata files ..."

diffoscope --html-dir diffoscope metadata.0 metadata.1 \
        --max-diff-block-lines 5000 \
        --max-diff-input-lines 10000000 \
        --max-report-size 204800000