getcwd returns incorrect answer using OPFS with WASMFS

[rickg-hcl]

Please include the following in your bug report:

Version of emscripten/emsdk:
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.6 (1ddaae4)
clang version 21.0.0git (https:/github.com/llvm/llvm-project 4775e6d9099467df9363e1a3cd5950cc3d2fde05)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /Users/richardgillaspy/GitHubOpen/emsdk/upstream/bin
Full link command and output with -v appended:
emcc -g -v -s WASMFS -pthread -s PROXY_TO_PTHREAD=1 -s EXPORTED_FUNCTIONS='malloc,free' wasmfs_opfs_chdir.c -o test.html
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/bin/clang -target wasm32-unknown-emscripten -fignore-exceptions -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --sysroot=/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot -D__EMSCRIPTEN_SHARED_MEMORY=1 -DEMSCRIPTEN -Xclang -iwithsysroot/include/fakesdl -Xclang -iwithsysroot/include/compat -g3 -v -pthread -c wasmfs_opfs_chdir.c -o /var/folders/d8/08bv2b6s2b50q04__ln3cmbh0000gp/T/emscripten_temp_6oqmw94u/wasmfs_opfs_chdir_0.o
clang version 21.0.0git (https:/github.com/llvm/llvm-project 4775e6d9099467df9363e1a3cd5950cc3d2fde05)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /Users/richardgillaspy/GitHubOpen/emsdk/upstream/bin
(in-process)
"/Users/richardgillaspy/GitHubOpen/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 wasmfs_opfs_chdir.c -mrelocation-model static -mframe-pointer=none -ffp-contract=on -fno-rounding-math -mconstructor-aliases -target-feature +atomics -target-feature +bulk-memory -target-feature +mutable-globals -target-feature +sign-ext -target-cpu generic -fvisibility=hidden -debug-info-kind=constructor -dwarf-version=4 -debugger-tuning=gdb -fdebug-compilation-dir=/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/test -v -fcoverage-compilation-dir=/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/test -resource-dir /Users/richardgillaspy/GitHubOpen/emsdk/upstream/lib/clang/21 -D EMSCRIPTEN_SHARED_MEMORY=1 -D EMSCRIPTEN -isysroot /Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot -internal-isystem /Users/richardgillaspy/GitHubOpen/emsdk/upstream/lib/clang/21/include -internal-isystem /Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten -internal-isystem /Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/include -ferror-limit 19 -pthread -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fignore-exceptions -fcolor-diagnostics -iwithsysroot/include/fakesdl -iwithsysroot/include/compat -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -o /var/folders/d8/08bv2b6s2b50q04__ln3cmbh0000gp/T/emscripten_temp_6oqmw94u/wasmfs_opfs_chdir_0.o -x c wasmfs_opfs_chdir.c
clang -cc1 version 21.0.0git based upon LLVM 21.0.0git default target x86_64-apple-darwin23.6.0
ignoring nonexistent directory "/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten"
#include "..." search starts here:
#include <...> search starts here:
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/include/fakesdl
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/include/compat
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/lib/clang/21/include
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/include
End of search list.
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/bin/clang --version
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/bin/wasm-ld -o test.wasm /var/folders/d8/08bv2b6s2b50q04__ln3cmbh0000gp/T/emscripten_temp_6oqmw94u/wasmfs_opfs_chdir_0.o -L/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -L/Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/src/lib /Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/crtbegin.o /Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/crt1_proxy_main.o -lGL-mt-getprocaddr -lal -lhtml5 -lstubs-debug -lnoexit -lc-mt-debug -ldlmalloc-mt-debug -lcompiler_rt-mt -lc++-mt-noexcept -lc++abi-debug-mt-noexcept -lsockets-mt -lwasmfs_no_fs -lwasmfs-mt-debug -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr /var/folders/d8/08bv2b6s2b50q04__ln3cmbh0000gp/T/tmp0xbwqnvmlibemscripten_js_symbols.so --import-memory --shared-memory --export=malloc --export=free --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_init --export=wasmfs_flush --export=_emscripten_stack_alloc --export=_emscripten_thread_free_data --export=_emscripten_thread_crashed --export=__wasm_call_ctors --export=_emscripten_tls_init --export=_emscripten_thread_init --export=_emscripten_stack_restore --export=emscripten_stack_set_limits --export=_emscripten_thread_exit --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=fflush --export-table -z stack-size=65536 --no-growable-memory --initial-memory=16777216 --entry=_emscripten_proxy_main --stack-first --table-base=1
/Users/richardgillaspy/GitHubOpen/emsdk/upstream/bin/llvm-objcopy test.wasm test.wasm --remove-section=producers
emcc: warning: main is defined in the input files, but _main is not in EXPORTED_FUNCTIONS. Add it to this list if you want main to run. [-Wunused-main]
/Users/richardgillaspy/GitHubOpen/emsdk/node/20.18.0_64bit/bin/node /Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/tools/compiler.mjs -
/Users/richardgillaspy/GitHubOpen/emsdk/node/20.18.0_64bit/bin/node /Users/richardgillaspy/GitHubOpen/emsdk/upstream/emscripten/tools/preprocessor.mjs - shell.html

Note: Where possible, please avoid attaching screen shots of code or console
logs. Instead, please include them as text so that they may be copied /
searched. To make code blocks more readable and syntax highlighted, please
escape them with three backticks before and after, like this:

#include <assert.h>
#include <dirent.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>

#include <emscripten.h>
#include <emscripten/console.h>
#include <emscripten/wasmfs.h>


int main(int argc, char* argv[]) {
  int err, fd, nwritten;
  const char* msg = "Hello, OPFS!";
  const char* msg2 = "Hello, OPFS!Hello, OPFS!";

  emscripten_console_log("starting main");

  backend_t opfs = wasmfs_create_opfs_backend();
  emscripten_console_log("created OPFS backend");

  err = wasmfs_create_directory("/opfs", 0777, opfs);
  assert(err == 0);
  emscripten_console_log("mounted OPFS root directory");

  mkdir("/opfs/data", 0777);
  symlink("/opfs/data", "/data");

  chdir("/opfs");
  char CWD[100] = {};
  getcwd(CWD, sizeof(CWD));
  emscripten_console_logf("CWD: %s", CWD);
  assert(strcmp(CWD, "/opfs") == 0); // fail, result is '/' should be '/opfs'


   chdir("/data");
   getcwd(CWD, sizeof(CWD));
   emscripten_console_logf("CWD: %s", CWD);
   assert(strcmp(CWD, "/data") == 0); // fail, result is '//data' should be '/data'
} 

[sbc100]

Is this a duplicate of #18112?