- echo "// __cxa_thread_atexit_impl is used to more effeciently cleanup per-thread local storage by rust libstd." >> src/main/jni/bindings.c
- echo "// However, it is not available on glibc versions 2.17 or earlier, and rust libstd has a null-check and fallback in case it is missing." >> src/main/jni/bindings.c
- echo "// Because it is weak-linked on the rust side, we can simply define it explicitly here, forcing rust to use the fallback." >> src/main/jni/bindings.c
- echo "void *__cxa_thread_atexit_impl = NULL;" >> src/main/jni/bindings.c
+ # __cxa_thread_atexit_impl is used to more effeciently cleanup per-thread local storage by rust libstd.
+ # However, it is not available on glibc versions 2.17 or earlier, and rust libstd has a null-check and
+ # fallback in case it is missing.
+ # Because it is weak-linked on the rust side, we should be able to simply define it
+ # explicitly, forcing rust to use the fallback. However, for some reason involving ancient
+ # dark magic and haunted code segments, overriding the weak symbol only impacts sites which
+ # *call* the symbol in question, not sites which *compare with* the symbol in question.
+ # This means that the NULL check in rust's libstd will always think the function is
+ # callable while the function which is called ends up being NULL (leading to a jmp to the
+ # zero page and a quick SEGFAULT).
+ # This issue persists not only with directly providing a symbol, but also ld.lld's -wrap
+ # and --defsym arguments.
+ # In smaller programs, it appears to be possible to work around this with -Bsymbolic and
+ # -nostdlib, however when applied the full-sized JNI library here it no longer works.
+ # After exhausting nearly every flag documented in lld, the only reliable method appears
+ # to be editing the LDK binary. Luckily, LLVM's tooling makes this rather easy as we can
+ # disassemble it into very readable code, edit it, and then reassemble it.
+ # Note that if we do so we don't have to bother overriding the actual call, LLVM should
+ # optimize it away, which also provides a good check that there isn't anything actually
+ # relying on it elsewhere.
+ [ ! -f "$1"/lightning-c-bindings/target/$LDK_TARGET/release/libldk.a ] && exit 1
+ if [ "$(ar t "$1"/lightning-c-bindings/target/$LDK_TARGET/release/libldk.a | grep -v "\.o$" || echo)" != "" ]; then
+ echo "Archive contained non-object files!"
+ exit 1
+ fi
+ if [ "$(ar t "$1"/lightning-c-bindings/target/$LDK_TARGET/release/libldk.a | grep ldk.ldk.*-cgu.*.rcgu.o | wc -l)" != "1" ]; then
+ echo "Archive contained more than one LDK object file"
+ exit 1
+ fi
+ mkdir -p tmp
+ rm -f tmp/*
+ ar x --output=tmp "$1"/lightning-c-bindings/target/$LDK_TARGET/release/libldk.a
+ pushd tmp
+ llvm-dis ldk.ldk.*-cgu.*.rcgu.o
+ sed -i 's/br i1 icmp eq (i8\* @__cxa_thread_atexit_impl, i8\* null)/br i1 icmp eq (i8* null, i8* null)/g' ldk.ldk.*-cgu.*.rcgu.o.ll
+ llvm-as ldk.ldk.*-cgu.*.rcgu.o.ll -o ./libldk.bc
+ ar q libldk.a *.o
+ popd
+ LDK_LIB="tmp/libldk.bc tmp/libldk.a"