Relative path lookups don't work anymore in a directory mounted with IDBFS with emscripten 3.1.74

[leopatras]

The attached program tries to lookup some relative existing pathes with FS.lookupPath() (see in pre.js)
There are 3 directories created

/app
/home
/persist

/app is in MEMFS, the 2 others mounted with IDBFS.
When FS.cwd() is in /home, the lookup for ../app fails.
This did work previously with emscripten 3.1.67, so the attached program runs without errors up to 3.1.73, but raises console.error since 3.1.74 .

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.5 (53b38d0c6f9fce1b62c55a8012bc6477f7a42711)
clang version 21.0.0git (https:/github.com/llvm/llvm-project 553da9634dc4bae215e6c850d2de3186d09f9da5)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /Users/leo/w/github/emsdk/upstream/bin

Full link command and output with -v appended:

emcc -v \
         -O2 \
         --pre-js pre.js \
         -s MAIN_MODULE=1 \
         -s FORCE_FILESYSTEM=1 \
         -s EXPORT_ALL=1 \
         -s ASSERTIONS=1 \
         -s STACK_SIZE=200000 \
         -s SAFE_HEAP \
         -s ASYNCIFY \
         -s ASYNCIFY_STACK_SIZE=200000 \
         -s MAXIMUM_MEMORY=4GB \
         -s STACK_OVERFLOW_CHECK=2 \
         -s EXIT_RUNTIME=1 \
         -s ALLOW_MEMORY_GROWTH=1 \
 -lidbfs.js \
 -lproxyfs.js \
          main.c -o main.html
/Users/leo/w/github/emsdk/upstream/bin/clang -target wasm32-unknown-emscripten -fignore-exceptions -fPIC -fvisibility=default -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --sysroot=/Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot -DEMSCRIPTEN -Xclang -iwithsysroot/include/fakesdl -Xclang -iwithsysroot/include/compat -v -O2 -c main.c -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main_0.o
clang version 21.0.0git (https:/[github.com/llvm/llvm-project](http://github.com/llvm/llvm-project) 553da9634dc4bae215e6c850d2de3186d09f9da5)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /Users/leo/w/github/emsdk/upstream/bin
(in-process)
"/Users/leo/w/github/emsdk/upstream/bin/clang-21" -cc1 -triple wasm32-unknown-emscripten -emit-obj -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name main.c -mrelocation-model pic -pic-level 2 -mframe-pointer=none -ffp-contract=on -fno-rounding-math -mconstructor-aliases -target-feature +mutable-globals -target-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/Users/leo/w/gwa/test/mountproblem -v -fcoverage-compilation-dir=/Users/leo/w/gwa/test/mountproblem -resource-dir /Users/leo/w/github/emsdk/upstream/lib/clang/21 -D EMSCRIPTEN -isysroot /Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot -I/usr/local/include -internal-isystem /Users/leo/w/github/emsdk/upstream/lib/clang/21/include -internal-isystem /Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten -internal-isystem /Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot/include -O2 -ferror-limit 19 -fvisibility=default -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fignore-exceptions -fcolor-diagnostics -vectorize-loops -vectorize-slp -iwithsysroot/include/fakesdl -iwithsysroot/include/compat -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main_0.o -x c main.c
clang -cc1 version 21.0.0git based upon LLVM 21.0.0git default target x86_64-apple-darwin24.3.0
ignoring nonexistent directory "/Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot/include/fakesdl
/Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot/include/compat
/Users/leo/w/github/emsdk/upstream/lib/clang/21/include
/Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot/include
End of search list.
/Users/leo/w/github/emsdk/upstream/bin/clang --version
/Users/leo/w/github/emsdk/upstream/bin/wasm-ld -o main.wasm --whole-archive /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main_0.o -L/Users/leo/w/github/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/pic -L/Users/leo/w/github/emsdk/upstream/emscripten/src/lib -lGL-getprocaddr -lal -lhtml5 -lstubs-debug -lc-debug -ldlmalloc-debug -lcompiler_rt -lc++-noexcept -lc++abi-debug-noexcept -lsockets --no-whole-archive -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --export-if-defined=setThrew --export-if-defined=_emscripten_stack_restore --export-if-defined=emscripten_stack_get_current --export-if-defined=calloc --export-if-defined=strerror --export-if-defined=malloc --export-if-defined=free --export-if-defined=_emscripten_stack_alloc --export-if-defined=_emscripten_tempret_get --export-if-defined=_emscripten_tempret_set --export-if-defined=htons --export-if-defined=ntohs --export-if-defined=htonl --export-if-defined=_emscripten_timeout --export-if-defined=emscripten_stack_get_base --export-if-defined=emscripten_stack_get_end --export-if-defined=__cxa_can_catch --export-if-defined=__cxa_increment_exception_refcount --export-if-defined=__cxa_get_exception_ptr --export-if-defined=__cxa_decrement_exception_refcount --export-if-defined=fileno --export-if-defined=emscripten_builtin_memalign --export-if-defined=__dl_seterr --export-if-defined=memcmp --export-if-defined=memcpy --export-if-defined=emscripten_stack_set_limits --export-if-defined=realloc --export-if-defined=__errno_location --export-if-defined=__cxa_demangle /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/tmp7h4taxczlibemscripten_js_symbols.so --import-memory --export-dynamic --export=sbrk --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_set_limits --export=_emscripten_stack_alloc --export=emscripten_get_sbrk_ptr --export=__funcs_on_exit --export=__wasm_call_ctors --export=setThrew --export=_emscripten_stack_restore --export=calloc --export=strerror --export=malloc --export=free --export=_emscripten_tempret_get --export=_emscripten_tempret_set --export=htons --export=ntohs --export=htonl --export=_emscripten_timeout --export=__cxa_can_catch --export=__cxa_increment_exception_refcount --export=__cxa_get_exception_ptr --export=__cxa_decrement_exception_refcount --export=fileno --export=emscripten_builtin_memalign --export=__dl_seterr --export=memcmp --export=memcpy --export=realloc --export=__errno_location --export=__cxa_demangle --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-if-defined=main --export-if-defined=__main_argc_argv --export-if-defined=__wasm_apply_data_relocs --export-if-defined=fflush --experimental-pic --unresolved-symbols=import-dynamic -pie -z stack-size=200000 --max-memory=4294967296 --initial-memory=16777216 --no-entry
/Users/leo/w/github/emsdk/upstream/bin/llvm-objcopy main.wasm main.wasm --remove-section=.debug* --remove-section=producers --remove-section=name
/Users/leo/w/github/emsdk/upstream/bin/wasm-emscripten-finalize --bigint --no-legalize-javascript-ffi --check-stack-overflow main.wasm -o main.wasm --detect-features
/Users/leo/w/github/emsdk/upstream/bin/wasm-emscripten-finalize --bigint --no-legalize-javascript-ffi --check-stack-overflow main.wasm -o main.wasm --detect-features
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/compiler.mjs -
/Users/leo/w/github/emsdk/upstream/bin/wasm-opt --strip-target-features --safe-heap --post-emscripten -O2 --low-memory-unused --asyncify --pass-arg=asyncify-relocatable --pass-arg=asyncify-asserts --pass-arg=asyncify-propagate-addlist --pass-arg=asyncify-imports@env.invoke_*,env.__asyncjs__*,*.$asyncLoad,*.fd_sync,*.emscripten_promise_await,*.emscripten_async_load_script,*.emscripten_async_wget_data,*._dlopen_js,*.emscripten_idb_load,*.emscripten_idb_store,*.emscripten_idb_delete,*.emscripten_idb_exists,*.emscripten_idb_clear,*.emscripten_idb_load_blob,*.emscripten_idb_store_blob,*.emscripten_sleep,*.emscripten_wget_data,*.emscripten_scan_registers,*.emscripten_lazy_load_code,*._load_secondary_module,*.emscripten_fiber_swap,*.SDL_Delay --zero-filled-memory --pass-arg=directize-initial-contents-immutable main.wasm -o main.wasm --mvp-features --enable-bulk-memory --enable-bulk-memory-opt --enable-call-indirect-overlong --enable-multivalue --enable-mutable-globals --enable-nontrapping-float-to-int --enable-reference-types --enable-sign-ext
/Users/leo/w/github/emsdk/upstream/bin/wasm-opt --strip-target-features --safe-heap --post-emscripten -O2 --low-memory-unused --asyncify --pass-arg=asyncify-relocatable --pass-arg=asyncify-asserts --pass-arg=asyncify-propagate-addlist --pass-arg=asyncify-imports@env.invoke_*,env.__asyncjs__*,*.$asyncLoad,*.fd_sync,*.emscripten_promise_await,*.emscripten_async_load_script,*.emscripten_async_wget_data,*._dlopen_js,*.emscripten_idb_load,*.emscripten_idb_store,*.emscripten_idb_delete,*.emscripten_idb_exists,*.emscripten_idb_clear,*.emscripten_idb_load_blob,*.emscripten_idb_store_blob,*.emscripten_sleep,*.emscripten_wget_data,*.emscripten_scan_registers,*.emscripten_lazy_load_code,*._load_secondary_module,*.emscripten_fiber_swap,*.SDL_Delay --zero-filled-memory --pass-arg=directize-initial-contents-immutable main.wasm -o main.wasm --mvp-features --enable-bulk-memory --enable-bulk-memory-opt --enable-call-indirect-overlong --enable-multivalue --enable-mutable-globals --enable-nontrapping-float-to-int --enable-reference-types --enable-sign-ext
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.js unsignPointers -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso1.js
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.js unsignPointers -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso1.js
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso1.js safeHeap -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso2.js
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso1.js safeHeap -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso2.js
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso2.js --minify-whitespace -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso3.js
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/acorn-optimizer.mjs /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso2.js --minify-whitespace -o /var/folders/fv/7l4yvm9d2bvbsvl80kmhp8b40000gn/T/emscripten_temp_r00d263m/main.jso3.js
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/tools/preprocessor.mjs - shell.html
/Users/leo/tmp/node/bin/node /Users/leo/w/github/emsdk/upstream/emscripten/node_modules/.bin/html-minifier-terser main.html -o main.html --collapse-whitespace --remove-comments --remove-tag-whitespace --sort-attributes --sort-class-name --decode-entities --collapse-boolean-attributes --remove-attribute-quotes --remove-redundant-attributes --remove-script-type-attributes --remove-style-link-type-attributes --use-short-doctype --minify-css true --minify-js true

[leopatras]

Safari doesn't upload correctly (eye-roll) so finally the program attachment only done successfully with Chrome: lookup_rel.zip

[kripken]

It sounds like this is a regression. Then it could be good to bisect to see where it broke:

https://emscripten.org/docs/contributing/developers_guide.html#bisecting

[leopatras]

Thanks Alon, it did break in 3.1.74 , 3.1.73 is the last working version.
Regards, Leo

[sbc100]

@hoodmane has been doing a lot of FS work recently. Maybe this looks familiar?

@leopatras you should be able to track it down to a narrower change (a single emscripten-releases commit) if you have time to continue bisecting.

[hoodmane]

I haven't checked but I'm pretty sure it's due to this change:
https://github.com/emscripten-core/emscripten/pull/23072/files#diff-d811c380254a6bcd9b4fd6a89f7848d7708f7de78c521f65fae2ae352931acfeR200
Probably because:

current = current.parent;

cannot go above the root of an FS mount point?

[hoodmane]

Yeah for the mountpoint current.parent === current. So I guess that line should instead be:

   if (FS.isMountpoint(current)) {
      // if we're at a mount we have no way to get to the parent directly, so we have to start over.
      current = FS.lookupPath(current_path).node;
   } else {
      current = current.parent;
   }

[hoodmane]

Unfortunate to have to add another recursive call to lookupPath in there, but at least we know there are no symlinks or weird stuff in that part of the path I think.

[hoodmane]

Okay opened #23990 with a fix. Thanks for the report @leopatras!

[leopatras]

Wow, that was quick! Thanks a lot @hoodmane !