test.c

#define NUM 16

int foo[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
int *bar = ((int *)&foo) + NUM;

test.sh

#!/usr/bin/env bash

set -eu

CC="clang --target=wasm32-unknown-unknown-wasm -nostdlib"
$CC -c test.c  -o test1.o
$CC -r test1.o -o test2.o
$CC -r test2.o -o test3.o

Output:

lld: error: unexpected existing value for R_WEBASSEMBLY_MEMORY_ADDR_I32: existing=64 expected=4294967232
clang-7: error: lld command failed with exit code 1 (use -v to see invocation)

Interestingly, whether or not this breaks depends on that NUM being 16. If NUM >= 16 && NUM < 32, it breaks. But if NUM < 16 || NUM >= 32, it works. EDIT: "works" as in it exits cleanly; I guess I'm not really sure how to verify that it's correct.

Fix is here: https://reviews.llvm.org/D45825. Thanks for tracking that down!