wasm-backend: Code compiled with fPIC is not compatible with regular executables

[sbc100]

See the corresponding upstream llvm issue: https://bugs.llvm.org/show_bug.cgi?id=42656

[dstaley]

Question: if I'm getting output like

error: undefined symbol: g$bio_lookup_lock
error: undefined symbol: g$bio_type_lock
error: undefined symbol: g$stderr
error: undefined symbol: __memory_base
error: undefined symbol: __table_base

That's most likely related to this issue, correct? Looking at the other unexported symbols it appears it's due to my build of OpenSSL, which I'm 90% sure I disabled fPIC on. If it's possible this isn't an fPIC issue I'd be happy to file a new issue, but I just wanted to check before I did so.

[kripken]

@dstaley correct, that looks like the errors currently expected due to this bug. (If you verify you are not passing fPIC though, then please provide a testcase, as it may be there is another bug with the same symptoms.)

[sbc100]

Should be fixed once this lands: https://reviews.llvm.org/D65922

[remoe]

I've tested LLVM 032e1fdcd47ef98936c88aa30571c6a713179a46 with a build of https://zlib.net/zlib-1.2.11.tar.gz . It throws:

emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o adler32.o adler32.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o crc32.o crc32.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o deflate.o deflate.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o infback.o infback.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o inffast.o inffast.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o inflate.o inflate.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o inftrees.o inftrees.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o trees.o trees.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o zutil.o zutil.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o compress.o compress.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o uncompr.o uncompr.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o gzclose.o gzclose.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o gzlib.o gzlib.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o gzread.o gzread.c
emscripten-1.38.41/emcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -c -o gzwrite.o gzwrite.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/adler32.o adler32.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/crc32.o crc32.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/deflate.o deflate.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/infback.o infback.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/inffast.o inffast.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/inflate.o inflate.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/inftrees.o inftrees.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/trees.o trees.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/zutil.o zutil.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/compress.o compress.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/uncompr.o uncompr.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/gzclose.o gzclose.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/gzlib.o gzlib.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/gzwrite.o gzwrite.c
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN  -DPIC -c -o objs/gzread.o gzread.c
emscripten-1.38.41/emar rc libz.a adler32.o crc32.o deflate.o infback.o inffast.o inflate.o inftrees.o trees.o zutil.o compress.o uncompr.o gzclose.o gzlib.o gzread.o gzwrite.o
emscripten-1.38.41/emcc -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN -o libz.so.1.2.11 adler32.lo crc32.lo deflate.lo infback.lo inffast.lo inflate.lo inftrees.lo trees.lo zutil.lo compress.lo uncompr.lo gzclose.lo gzlib.lo gzread.lo gzwrite.lo  -lc



wasm-ld: /llvm-10.0/llvm-project.git/lld/wasm/Symbols.cpp:115: void lld::wasm::Symbol::setGOTIndex(uint32_t): Assertion `gotIndex == INVALID_INDEX' failed.
Stack dump:
0.      Program arguments: /llvm-10.0/bin/wasm-ld -o libz.so.1.2.11 --allow-undefined --import-memory --import-table --lto-O0 adler32.lo crc32.lo deflate.lo infback.lo inffast.lo inflate.lo inftrees.lo trees.lo zutil.lo compress.lo uncompr.lo gzclose.lo gzlib.lo gzread.lo gzwrite.lo -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --export __wasm_call_ctors --export __data_end --export main --export malloc --export free --export setThrew --export __errno_location -z stack-size=5242880 --initial-memory=16777216 --no-entry --max-memory=16777216 --global-base=1024 --relocatable
 #0 0x00007fd2cb76c1f9 llvm::sys::PrintStackTrace(llvm::raw_ostream&) /llvm-10.0/llvm-project.git/llvm/lib/Support/Unix/Signals.inc:532:0
 #1 0x00007fd2cb76c28c PrintStackTraceSignalHandler(void*) /llvm-10.0/llvm-project.git/llvm/lib/Support/Unix/Signals.inc:593:0
 #2 0x00007fd2cb76a15b llvm::sys::RunSignalHandlers() /llvm-10.0/llvm-project.git/llvm/lib/Support/Signals.cpp:68:0
 #3 0x00007fd2cb76bbb0 SignalHandler(int) /llvm-10.0/llvm-project.git/llvm/lib/Support/Unix/Signals.inc:384:0
 #4 0x00007fd2cadf2890 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
 #5 0x00007fd2c9eaee97 raise /build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #6 0x00007fd2c9eb0801 abort /build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
 #7 0x00007fd2c9ea039a __assert_fail_base /build/glibc-OTsEL5/glibc-2.27/assert/assert.c:89:0
 #8 0x00007fd2c9ea0412 (/lib/x86_64-linux-gnu/libc.so.6+0x30412)
 #9 0x00007fd2cbb82930 lld::wasm::Symbol::setGOTIndex(unsigned int) /llvm-10.0/llvm-project.git/lld/wasm/Symbols.cpp:116:0
#10 0x00007fd2cbba5b0b lld::wasm::GlobalSection::assignIndexes() /llvm-10.0/llvm-project.git/lld/wasm/SyntheticSections.cpp:243:0
#11 0x00007fd2cbb88fdd (anonymous namespace)::Writer::assignIndexes() /llvm-10.0/llvm-project.git/lld/wasm/Writer.cpp:624:0
#12 0x00007fd2cbb8ad23 (anonymous namespace)::Writer::run() /llvm-10.0/llvm-project.git/lld/wasm/Writer.cpp:899:0
#13 0x00007fd2cbb8b7f0 lld::wasm::writeResult() /llvm-10.0/llvm-project.git/lld/wasm/Writer.cpp:983:0
#14 0x00007fd2cbb54594 (anonymous namespace)::LinkerDriver::link(llvm::ArrayRef<char const*>) /llvm-10.0/llvm-project.git/lld/wasm/Driver.cpp:791:0
#15 0x00007fd2cbb4fad7 lld::wasm::link(llvm::ArrayRef<char const*>, bool, llvm::raw_ostream&) /llvm-10.0/llvm-project.git/lld/wasm/Driver.cpp:95:0
#16 0x00007fd2cb6fa9e5 main /llvm-10.0/llvm-project.git/lld/tools/lld/lld.cpp:159:0
#17 0x00007fd2c9e91b97 __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
#18 0x00007fd2cb6f9b2a _start (/llvm-10.0/bin/wasm-ld+0x2f9b2a)
shared:ERROR: '/llvm-10.0/bin/wasm-ld -o libz.so.1.2.11 --allow-undefined --import-memory --import-table --lto-O0 adler32.lo crc32.lo deflate.lo infback.lo inffast.lo inflate.lo inftrees.lo trees.lo zutil.lo compress.lo uncompr.lo gzclose.lo gzlib.lo gzread.lo gzwrite.lo -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --export __wasm_call_ctors --export __data_end --export main --export malloc --export free --export setThrew --export __errno_location -z stack-size=5242880 --initial-memory=16777216 --no-entry --max-memory=16777216 --global-base=1024 --relocatable' failed (-6)
Makefile:282: recipe for target 'libz.so.1.2.11' failed```

[sbc100]

Should be fixed in https://reviews.llvm.org/D66435