WebAssembly/Roadmap

Short-Term

These steps are critical for completion in order to have wasm a full scope CPU target for FPC compiler

Feature	Status	Description
Assembly (textual wasm)	working	Pick an assembler utility that's sequence instruction (FPC) friendly FPC should produce a textual assembly file. Currently, FPC uses the LLVM assembler llvm-mc.
Linking	working	Pick an linker utility that's sequence instruction (FPC) friendly. Linker is a moving target. As a new feature is added, the linking needs to be re-verified. Currently, FPC uses the LLVM linker.
Basic function calls and local variables	working	Implement direct function calls, with passing basic parameters (that don't require any memory. I.e. int and floats)
Verify float-point values	working	As the float points are being converted from the textual format. It's necessary to make sure that the proper values are generated. As of now, they appear to work, including + or - infinity and NaNs.
Global variables	working	Implement symbol reference to global variables (basic or complex) Consider linking - as the index of symbols can change. (Wasm binaries are index based )
Stack/Call frame support	working	WebAssembly doesn't have any native stack and/or frame support. It has to be emulated using global and local variables. Blocking issue: https://github.com/WebAssembly/wabt/issues/1199
Indirect function calls	working	WebAssembly has a specific way of indirect calls Needed for vmt and procedure variables (callback) calls
VMT	working	Support for calls via virtual method table
RTL.Memory Manager	working
RTL.(Ansi/Wide) String Manager	working
RTL.WASI.Console I/O	working	Standard input, standard output and error output (stderr) works on the WASI target.
RTL.WASI.Command line parameters	working	Both ParamStr and ParamCount work.
RTL.WASI.Exit codes	working	Terminating the program with an exit code via halt(XXX) works.
RTL.WASI.Randomize	working
RTL.WASI.File I/O	in progress	The WASI target needs a mechanism for converting path names (both relative and absolute) to paths, relative to a given set of preopened directories (these are the directories you're given access to). Also, the concept of current directory needs to be emulated, too. This is partially implemented now, although changing the current directory is not yet implemented. Relevant upstream development to follow: [1]
RTL.WASI.File I/O.Basic File I/O	working	This covers basic sequential reading and writing of text and binary files. This includes Assign, Reset, Rewrite, Append, Close, Read, Write, Readln, Writeln, EoF, EoLn, BlockRead, BlockWrite.
RTL.WASI.File I/O.ChDir	in progress	Partially working. Needs more testing. Things left TODO: #1: in case there's no mapping for '/', support ChDir to the upper unmapped parts of a mapped directory, e.g. if the user has mapped only '/home/someuser', support ChDir to '/' and '/home' as well. TODO #2: check how Windows paths are implemented and support that, e.g. if needed, support and test paths with drive names e.g. 'C:\'. Also support paths with backslashes as well as forward slashes, etc.
RTL.WASI.File I/O.MkDir	working
RTL.WASI.File I/O.RmDir	working
RTL.WASI.File I/O.GetDir	working
RTL.WASI.File I/O.Erase	working
RTL.WASI.File I/O.Rename	working
RTL.WASI.File I/O.Seek	working
RTL.WASI.File I/O.FileSize	working
RTL.WASI.File I/O.FilePos	working
RTL.WASI.File I/O.Truncate	working
RTL.WASI.DOS.FindFirst/FindNext/FindClose	working
RTL.WASI.DOS.Environment variables	working	This includes the environment variables of the DOS unit: GetEnv, EnvCount, EnvStr.
RTL.WASI.DOS.GetDate/GetTime	working	Works, but returns UTC time, instead of local time, because WASI lacks timezone support.
RTL.WASI.DOS.GetMsCount	working
RTL.WASI.DOS.GetFTime	working	Works, but returns UTC time, instead of local time, because WASI lacks timezone support.
RTL.WASI.DOS.SetFTime	not implemented	Not yet implemented.
RTL.WASI.DOS.GetFAttr	not implemented	Not yet implemented.
RTL.WASI.DOS.SetFAttr	not implemented	Not yet implemented.
RTL.WASI.DOS.FSearch	not implemented	Not yet implemented.
RTL.WASI.SysUtils unit	in progress	Unit compiles, but is untested. The file operations are not yet implemented.
RTL.WASI.SysUtils.Platform independent utilities	working	This includes various string and pchar utilities, type helpers, conversion routines (e.g. Format, Trim, IntToStr, StrToInt, ...), generic (not related to the system clock) utilities (e.g. IsLeapYear), etc.
RTL.WASI.SysUtils.File I/O	in progress
RTL.WASI.SysUtils.File I/O.FileOpen	working	Implemented. Note: Sharing/locking is not supported on WASI. Feature request is here: [2]
RTL.WASI.SysUtils.File I/O.FileCreate	working	Implemented. Note: Sharing/locking and Unix-style permissions are not supported on WASI.
RTL.WASI.SysUtils.File I/O.FileClose	working
RTL.WASI.SysUtils.File I/O.FileRead	working
RTL.WASI.SysUtils.File I/O.FileWrite	working
RTL.WASI.SysUtils.File I/O.FileSeek	working
RTL.WASI.SysUtils.File I/O.FileTruncate	working
RTL.WASI.SysUtils.File I/O.DirectoryExists	not implemented
RTL.WASI.SysUtils.File I/O.FileExists	working
RTL.WASI.SysUtils.File I/O.FileAge	working	Works, but returns UTC time, instead of local time, because WASI lacks timezone support.
RTL.WASI.SysUtils.File I/O.FileGetSymLinkTarget	not implemented
RTL.WASI.SysUtils.File I/O.FindFirst/FindNext/FindClose	not implemented
RTL.WASI.SysUtils.File I/O.FileGetDate	working	Works, but returns UTC time, instead of local time, because WASI lacks timezone support.
RTL.WASI.SysUtils.File I/O.FileSetDate	working	Works, but accepts UTC time, instead of local time, because WASI lacks timezone support.
RTL.WASI.SysUtils.File I/O.FileGetAttr	not implemented
RTL.WASI.SysUtils.File I/O.FileSetAttr	not implemented
RTL.WASI.SysUtils.File I/O.DeleteFile	working
RTL.WASI.SysUtils.File I/O.RenameFile	working
RTL.WASI.SysUtils.DiskFree	not implemented
RTL.WASI.SysUtils.DiskSize	not implemented
RTL.WASI.SysUtils.Environment variables	working
RTL.WASI.SysUtils.Sleep	working
RTL.WASI.SysUtils.Date and time functions, related to the system clock	not implemented
RTL.WASI.SysUtils.GetTickCount/GetTickCount64	working
RTL.WASI.Classes unit	working	Compiles and appears to be working. Needs more testing. Enabling one of the exception handling modes is highly recommended.

Long-Term

Future improvements for wasm target. Some of those are nice to have, but not critical. Others are difficult to implement or need features of WebAssembly, which haven't been standardized yet.

Feature	Status	Description
Debug Info	in progress	There's experimental DWARF support for WebAssembly, but it isn't working yet and the debugging tools for WebAssembly aren't very mature at this point even for C and C++. There's an LLVM linker bug, related to generating linker map files: [3]
Internal Object Writer	working	Enabled by default in commit bc76487b878e59133ce3c2cc19ebb13f9a9826ea
Internal Linker	not implemented
GOTO support	not implemented	Goto is difficult to implement, due to WebAssembly's lack of labels and jumps. It requires all gotos to be converted to structured flow, such as loops and break/continue. This requires implementing a complex algorithm, such as Relooper or Stackifier. Useful read: [4]
Exceptions support (no exceptions mode)	working	By default, exceptions are disabled. However, try..finally blocks still work and execute their finally section, even when using the 'exit', 'break' or 'continue' statements. Try..except blocks are compiled, however the 'except' part is never executed. And invoking 'raise' terminates the program, since exceptions cannot be caught in this mode.
Exceptions support (native exceptions mode)	working	Requires the exception handling proposal: [5] Information about the browser support for this new experimental feature is available here: [6]
Exceptions support (branchful exceptions mode)	working	This is a compatibility mode, that implements exception support by adding branching after each function call. This incurs a large runtime cost, but is compatible with all WebAssembly implementations and doesn't require the WebAssembly implementation to be JavaScript hosted. This is the only approach, that currently works with wasmtime.
Exceptions support (JavaScript-based exceptions handling mode)	not implemented	This is the compatibility mode, used by Emscripten. This also incurs a runtime cost, and also requires the WebAssembly implementation to be JavaScript-based, so this is not supported by wasmtime. In this mode, each function call inside a try block is wrapped inside a JavaScript function call, that wraps the WebAssembly function in a try .. catch JavaScript statement block.
Timezone support	not implemented	WASI currently lacks timezone support. This also applies to WASI's C library in the official SDK. It is possible to parse the TZ environment variable, and read the binary timezone data from the file system, in case that is accessible, however this is probably not portable, and isn't done by their C library. Upstream bug reports: [7] [8] [9]
Multithreading support	not implemented	Threads are not supported in WebAssembly MVP. There is a future proposal here: [10] It is already implemented in most browsers: [11] However, it is not yet supported by WASI and wasmtime, so there's no spec or API for creating threads.
Process support - RTL.WASI.DOS.Exec/DosExitCode, fcl-process, etc.	not implemented	WASI does not support starting processes, yet. Proposal is here: [[12]]
RTL.WASI.DOS.DiskFree	not implemented	Not sure if supported by the WASI API. Can be implemented, if an appropriate WASI API is added in the future.
RTL.WASI.DOS.DiskSize	not implemented	Not sure if supported by the WASI API. Can be implemented, if an appropriate WASI API is added in the future.
RTL.WASI.DOS.SetDate/SetTime	not implemented	Setting the system clock is not supported by the WASI API. Can be implemented, if an appropriate WASI API is added in the future.

See Also

• WebAssembly