undefined symbol: wcsftime

[tiran]

Please include the following in your bug report:

Emscripten's libc is missing wcsftime function although the source file https://github.com/emscripten-core/emscripten/blob/3.1.1/system/lib/libc/musl/src/time/wcsftime.c is shipped with emsdk. A similar issue was reported in #7057, but the bug was auto-closed.

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.1 (1934a98e709b57d3592b8272d3f1264a72c089e4)
clang version 14.0.0 (https://github.com/llvm/llvm-project f142c45f1e494f8dbdcc1bcf14122d128ac8f3fe)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /emsdk/upstream/bin

Failing command line in full:

configure:13727: /emsdk/upstream/emscripten/emcc -o conftest    conftest.c -ldl  >&5
error: undefined symbol: wcsftime (referenced by top-level compiled C/C++ code)
warning: Link with `-s LLD_REPORT_UNDEFINED` to get more information on undefined symbols
warning: To disable errors for undefined symbols use `-s ERROR_ON_UNDEFINED_SYMBOLS=0`
warning: _wcsftime may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
Error: Aborting compilation due to previous errors
emcc: error: '/emsdk/node/14.18.2_64bit/bin/node /emsdk/upstream/emscripten/src/compiler.js /tmp/tmplokibpqr.json' failed (returned 1)
configure:13727: $? = 1

I noticed that libc.a does not include the object file for wcsftime.c:

# /emsdk/upstream/bin/llvm-ar t /emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/libc.a | grep wcsftime
# echo $?
1
# /emsdk/upstream/bin/llvm-ar t /emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/libc.a | grep wcs
mbsnrtowcs.o
mbsrtowcs.o
mbstowcs.o
wcscasecmp.o
wcscasecmp_l.o
wcscat.o
wcschr.o
wcscmp.o
wcscoll.o
wcscpy.o
wcscspn.o
wcsdup.o
wcslen.o
wcsncasecmp.o
wcsncasecmp_l.o
wcsncat.o
wcsncmp.o
wcsncpy.o
wcsnlen.o
wcsnrtombs.o
wcspbrk.o
wcsrchr.o
wcsrtombs.o
wcsspn.o
wcsstr.o
wcstod.o
wcstok.o
wcstol.o
wcstombs.o
wcswcs.o
wcswidth.o
wcsxfrm.o

[kripken]

Looking into this, the tricky part is that musl's wcsftime depends on an internal function in strftime, specifically __strftime_fmt_1. We actually implement strftime in JS, so that file is not included, and so just including wcsftime.c is not enough.

To fix this we could either split that helper function out to a separate file that is in the link, or we could look into moving strftime into musl (which would be a larger refactoring).

[tiran]

Ah, you are using a JS implementation of strftime. That might explain why we are getting different outputs in Python port to Emscripten. I thought it was caused by missing wcsftime. The JS implementation seems to be missing some special format cases:

Python on glibc or musl

>>> import datetime
>>> datetime.date(2022, 1, 1).strftime("%Y.%-m.%-d")
'2022.1.1'

Python wasm32-emscripten in node

>>> import datetime
>>> datetime.date(2022, 1, 1).strftime("%Y.%-m.%-d")
'2022.%-m.%-d'

[tiran]

I'm closing my feature request. We don't require wcsftime in CPython. The actual issue is #16156.