My goal is to compile my C program to wasm with emscripten (which I installed via emsdk). It uses libxml2. I am following the steps outlined here https://github.com/kripken/xml.js/blob/master/script/libxml2 to build
libxml2 from source with the appropriate emscripten parameters.
When I run emmake make, I get the following warnings and errors:
...
CCLD libxml2.la
emcc: warning: linking a library with `-shared` will emit a static object file.
This is a form of emulation to support existing build systems.
If you want to build a runtime shared library use the SIDE_MODULE setting. [-Wemcc]
emcc: warning: ignoring unsupported linker flag: `--version-script=./libxml2.syms` [-Wlinkflags]
wasm-ld: error: cannot open libxml2.so.2: No such file or directory
emcc: error: '/home/willy/emsdk/upstream/bin/wasm-ld -o .libs/libxml2.so.2.9.9 .libs/SAX.o .libs/entities.o .libs/encoding.o -L/home/willy/emsdk/upstream/emscripten/system/local/lib .libs/error.o -L/home/willy/emsdk/upstream/emscripten/system/lib .libs/parserInternals.o -L/home/willy/emsdk/upstream/emscripten/cache/wasm .libs/parser.o .libs/tree.o .libs/hash.o .libs/list.o .libs/xmlIO.o .libs/xmlmemory.o .libs/uri.o .libs/valid.o .libs/xlink.o .libs/HTMLparser.o .libs/HTMLtree.o .libs/debugXML.o .libs/xpath.o .libs/xpointer.o .libs/xinclude.o .libs/nanohttp.o .libs/nanoftp.o .libs/catalog.o .libs/globals.o .libs/threads.o .libs/c14n.o .libs/xmlstring.o .libs/buf.o .libs/xmlregexp.o .libs/xmlschemas.o .libs/xmlschemastypes.o .libs/xmlunicode.o .libs/xmlreader.o .libs/relaxng.o .libs/dict.o .libs/SAX2.o .libs/xmlwriter.o .libs/legacy.o .libs/chvalid.o .libs/pattern.o .libs/xmlsave.o .libs/xmlmodule.o .libs/schematron.o .libs/xzlib.o /home/willy/emsdk/upstream/emscripten/cache/wasm/libc.a libxml2.so.2 --relocatable -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr' failed (1)
make[2]: *** [Makefile:1065: libxml2.la] Error 1
make[2]: Leaving directory '/home/willy/CWasmSandbox/libxml2-2.9.9'
make[1]: *** [Makefile:1484: all-recursive] Error 1
make[1]: Leaving directory '/home/willy/CWasmSandbox/libxml2-2.9.9'
make: *** [Makefile:897: all] Error 2
The only thing I can gather with my limited understanding of emscripten is that it tries to access libxml2.so.2 which under normal circumstances would be generated from libxml2.la. But libxml2.so.2 was not generated because emscripten does not produce shared objects. Is this assesment correct? I tried passing the option CFLAGS="-s SIDE_MODULE=1" to make, but it didn't fix the error and was probably a stupid idea born from my limited knowledge of build systems. I also tried copying libxml2.so.2 from a previous installation into the appropriate directory, but no luck, and also kind of dumb since emscripten would have no use for .so files? What should my next steps be?
Easiest way is to resign from shared lib.
There is an important limitation with shared one (side module): it will not work if you are going to use threads in your main application.
So just make a change of ./script/libxml2
-emconfigure ../libxml2/configure --with-http=no --with-ftp=no --with-python=no --with-threads=no
+emconfigure ../libxml2/configure --with-http=no --with-ftp=no --with-python=no --with-threads=no --enable-shared=no
Build and link ./build/.libs/libxml2.a with your main application.