Undefined symbols for architecture arm64: _c_isdigit

[Jeffrey Walton]

Hi Everyone,

I'm trying to build libtasn1 4.16.0 with UBsan on a Mac-mini. I'm
catching a link error:

libtool: link: mv -f ".libs/libtasn1.expT" ".libs/libtasn1.exp"
libtool: link: sed 's|^|_|' < .libs/libtasn1.exp > .libs/libtasn1-symbols.expsym
libtool: link: /usr/bin/cc -dynamiclib  -o .libs/libtasn1.6.dylib
.libs/ASN1.o .libs/coding.o .libs/decoding.o .libs/element.o
.libs/errors.o .libs/gstr.o .libs/parser_aux.o .libs/structure.o
.libs/version.o   -Wl,-force_load,gl/.libs/libgnu.a
-L/Users/jwalton/ok2delete-ubsan/lib -ldl -lpthread  -g3 -O1
-fsanitize=undefined -arch arm64 -pthread -fsanitize=undefined
-Wl,-rpath -Wl,@loader_path/../lib -Wl,-rpath
-Wl,/Users/jwalton/ok2delete-ubsan/lib   -pthread -install_name
/Users/jwalton/ok2delete-ubsan/lib/libtasn1.6.dylib
-compatibility_version 13 -current_version 13.0 -Wl,-single_module
-Wl,-exported_symbols_list,.libs/libtasn1-symbols.expsym
Undefined symbols for architecture arm64:
  "_c_isdigit", referenced from:
      __asn1_expand_object_id in parser_aux.o
      __asn1_check_identifier in parser_aux.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1

It looks like c_isdigit is from Gnulib.
https://www.gnu.org/software/gnulib/manual/html_node/isdigit.html.

I'm not sure why the symbol is present during a regular link, but
missing under UBsan.

Does anyone know how to work around this issue?

Jeff