Build wasm

Start by reproducing the make command shown in the issue with the reported SQLite amalgamation and emcc version. Inspect src/api.js, src/exported_functions.json, and src/exported_runtime_methods.json alongside the Closure Compiler errors; done means the build completes successfully with the custom extension.

Hi there thanks for this great project!

I am building the Make File to load a custom SQLite extension.
Unfortunately the build fails. I have not modified the make file yet.
I think its emcc that's failing.

emcc --memory-init-file 0 -s RESERVED_FUNCTION_POINTERS=64 -s ALLOW_TABLE_GROWTH=1 -s EXPORTED_FUNCTIONS=@src/exported_functions.json -s EXPORTED_RUNTIME_METHODS=@src/exported_runtime_methods.json -s SINGLE_FILE=0 -s NODEJS_CATCH_EXIT=0 -s NODEJS_CATCH_REJECTION=0 -Oz -flto --closure 1 -s WASM=0 out/sqlite3.bc out/extension-functions.bc --pre-js src/api.js -o dist/sql-asm.js
building:ERROR: Closure compiler run failed:

building:ERROR: /tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:239:30: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. expected closing } See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  239|     @return {Database.SqlValue[]} One row of result
                                     ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:282:19: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. expected closing } See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  282|     @return {string[]} The names of the columns
                          ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:438:29: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. expected closing } See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  438|     @param {Database.SqlValue[]} values
                                    ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:438:29: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. expecting a variable name in a @param tag. See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  438|     @param {Database.SqlValue[]} values
                                    ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:588:20: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. expected closing } See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  588|     * @param {number[]} data An array of bytes representing
                           ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:588:20: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. expecting a variable name in a @param tag. See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  588|     * @param {number[]} data An array of bytes representing
                           ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:685:39: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. expected closing } See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  685|     * @return {Database.QueryExecResult[]} The results of each statement
                                              ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:736:42: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. missing closing ] See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  736|     @param {Statement.BindParams} [params=[]] Parameters to bind to the query
                                                 ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:927:22: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. missing opening ( See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  927|       @param {function} func the actual function to be executed.
                             ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:963:56: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. missing closing ] See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  963|       @param {function(): T} [aggregateFunctions.init = ()=>null]
                                                               ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:971:63: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. missing closing ] See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  971|       @param {function(T): any} [aggregateFunctions.finalize = (state)=>state]
                                                                      ^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:359:15: ERROR - [JSC_UNDEFINED_VARIABLE] variable allocate is undeclared
  359|   var strptr = allocate(bytes, ALLOC_NORMAL);
                      ^^^^^^^^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:359:31: ERROR - [JSC_UNDEFINED_VARIABLE] variable ALLOC_NORMAL is undeclared
  359|   var strptr = allocate(bytes, ALLOC_NORMAL);
                                      ^^^^^^^^^^^^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:693:20: ERROR - [JSC_UNDEFINED_VARIABLE] variable allocateUTF8OnStack is undeclared
  693|    var nextSqlPtr = allocateUTF8OnStack(sql);
                           ^^^^^^^^^^^^^^^^^^^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:812:40: ERROR - [JSC_UNDEFINED_VARIABLE] variable removeFunction is undeclared
  812|   Object.values(this.functions).forEach(removeFunction);
                                               ^^^^^^^^^^^^^^

/tmp/emscripten_temp_1_4iazly/sql-asm.jso4.js:945:17: ERROR - [JSC_UNDEFINED_VARIABLE] variable addFunction is undeclared
  945|   var func_ptr = addFunction(wrapped_func, "viii");
                        ^^^^^^^^^^^

5 error(s), 11 warning(s)

I'm building this version of sqlite https://www.sqlite.org/2022/sqlite-amalgamation-3390300.zip
on WSL and installed the latest version of emcc

Any clues on what's going wrong?