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Onramp Implementation Status

This is an incomplete list of features in C and related standards along with their implementation status in Onramp.

If a ✓ appears in the status column, the feature is implemented in Onramp. If a ½ appears in the status column, the feature is at least partially implemented, and may or may not be usable.

This is perhaps a wishlist of features that we'd like to implement, but it is in no way a promise or even a plan to implement them. Many of the features here will probably never be implemented. The main motivation for implementing features is whether real software we want to compile uses them.

Standards:

Onramp

This is mostly a list of internal Onramp features that still need to be implemented.

Virtual Machine

A feature is checked here if it is well-specified and it is implemented in the debugger and (for non-debug features) other common VMs.

Feature Status
Basic instruction set ✓
Command-line args, environment vars ✓
Syscall table, optional syscalls *
Syscalls: File I/O ✓
Syscalls: Stat
Syscalls: Directories
Syscalls: Symlinks
Syscalls: Time, Sleep ½
Syscalls: External Spawn
Interrupts, compare-and-swap
Debug info ½*
Stack traces ✓
Debugger single-stepping ✓
Debugger breakpoints
Profiling

* Syscalls are currently implemented as an instruction. This will be changed to a table of foreign function pointers where NULL can be used for unimplemented optional syscalls. This is the most pressing issue at the moment which is blocking many other features.

* Debug info works well in the c-debugger for a single program, but spawned programs are ignored. A new syscall is needed so that a program can inform the debugger when it loads another program.

Compiler

Feature Status
External zero/uninitialized storage (i.e. "bss")
RTL-style IR for optimization
Language standard selection (e.g. -std=c11)
Warning flags ½*
Rich error messages, notes *

* Parsing of warning flags mostly works but only in cci. It needs to be moved to libo and shared with cc and cpp.

* Rich error messages should print the stack of include files that led to a token and should display the source line of code with an arrow pointing to the column containing the error. This also needs to be moved to libo.

Preprocessor

Feature Status
Header guard optimization
Warnings

Linker

Feature Status
Constructors and destructors ✓
Weak symbols
Garbage collection

Standard Library

Feature Status
Software floating point

C89 (ANSI C)

Compiler

Feature Status
Basic integer types ✓
long long ✓
float, double *
Arrays ✓
Structs, unions ✓
Bitfields ½*
Enums ✓
Functions ✓
Function prototypes ✓
K&R-style functions
Function pointers ✓
Typedef ✓
Declarator parsing ✓
Arithmetic expressions ✓
Casts, implicit and explicit ✓
Address-of and dereference ✓
Passing structs by value ✓
Type promotion rules ✓
Functions ✓
Variadic functions ✓
Linkage specifiers ✓
if, else ✓
for, while, do ✓
switch, case, default ✓
Labels, goto ✓
Tentative definitions ✓
const checks ✓
Wide characters and strings (L prefix)
Initializers ½*
String escape sequences ✓
setjmp()/longjmp() ✓

* float and double support is mostly implemented in the compiler (except for floating-point literals) but it emits calls to libc functions that do not yet exist. Floating point arithmetic functions must be implemented in the libc; in the meantime it is not usable.

* Bitfields are parsed but ignored. This is a valid implementation of the spec, except for missing required diagnostics (e.g. preventing taking the address of a bitfield member.)

* Initializers are fully implemented and do work but they are grossly inefficient. A simple static array of char will emit initializaton bytecode an order of magnitude larger than the actual data. There is also no support yet for zero or uninitialized storage (i.e. there is no "bss" section.)

Preprocessor

Feature Status
Object-like macros ✓
Function-like macros ✓
Recursive macro expansion with hideset ✓
__FILE__, __LINE__ ✓
__DATE__, __TIME__
Stringify ✓
Token pasting ✓
#ifdef, #ifndef, #endif ✓
#if, #elif expression evaluation ✓
#include with macro expansion ✓

Standard Library

Feature Status
<stddef.h> basic types and macros ✓
Basic printing: fputs(), fputc(), etc. ✓
Strings: memcpy(), strncmp(), etc. ✓
Formatting: printf(), vsnprintf(), etc. ½*
Scanning: scanf(), sscanf(), etc.
File I/O: fopen(), fread(), etc. ✓
Memory allocation: malloc(), realloc(), etc. ✓
<math.h> functions
<errno.h> ✓
<stdlib.h> algorithms: qsort(), etc. ½
<ctype.h> character functions ✓
Signals: <signal.h>, sigaction(), raise()

* Basic printf() formatting works but specifier flags and modifiers are mostly ignored.

C95

No additional compiler features are necessary for C95. The C95 preprocessor and library additions are included under -std=c89.

Preprocessor

Feature Status
digraphs
__STDC_VERSION__

Standard Library

Feature Status
wide character support: <wchar.h>, <wctype.h>
wide character I/O
<iso646.h> alternate macros ✓

C99

Compiler

Feature Status
Mixed declarations and code ✓
for loop initializer ✓
Flexible array member ✓
Anonymous struct member ✓
_Bool ✓
__func__ ✓
inline *
restrict ✓*
Compound literals ✓
Variable-length arrays
Complex and imaginary numbers
Floating-point environment controls
static in array parameters
va_copy() ✓

* inline is ignored. This works fine for static inline but non-extern inline will have external definitions emitted which will cause linker errors.

* restrict is mostly ignored, which is valid except for the omission of required diagnostics.

Preprocessor

Feature Status
Line comments (//) ✓
Variadic macros ✓
_Pragma ✓

Standard Library

Feature Status
<stdint.h> ✓
<inttypes.h> ✓
<stdbool.h>, bool, true, false ✓
<complex.h> math functions
<tgmath.h>
<fenv.h>

C11

Compiler

Feature Status
Unicode string literals ?
Alignment specifiers, _Alignas and _Alignof
__typeof__
_Static_assert
_Atomic
_Thread_local
_Generic() expressions

Preprocessor

Feature Status
Feature test macros
Complex number construction: CMPLX(), etc.

Standard Library

Feature Status
aligned_alloc() ✓
<stdatomic.h>
<threads.h>

C17

C17 added no new features and only fixed C11 defects. In Onramp, C17 is an alias for C11; all C17 fixes are backported to C11.

C23

Compiler

Feature Status
[[attributes]]
Label without statement ?
Digit separator ✓
typeof, typeof_unqual
nullptr
Unicode identifiers ½*

* Unicode identifiers are generally supported but Onramp's set of identifier characters intentionally differs from Unicode Annex 31 in order to avoid a dependency on generated data tables.

Preprocessor

Feature Status
__has_c_attribute
__has_include
__has_embed
__has_builtin
#elifdef, #elifndef ✓
#warning ½
__VA_OPT__

Standard Library

Feature Status
<stdbit.h>
<stdckdint.h>
free_sized(), free_aligned_sized() ✓

C2Y

Compiler

Feature Status
defer (TS 25755) ✓

POSIX

POSIX features are activated by defining _POSIX_C_SOURCE before including any header files.

POSIX is huge, and Onramp will never be able to implement some parts of it (such as fork().) This is just a small subset of features, those we need or could conceivably implement in the near future.

Feature Status
I/O with file descriptors (open(), read(), etc.) ½
Symlinks (symlink(), lstat())
Terminal control (<termios.h>, fcntl() on stdin) ½
<sys/stat.h>: chmod(), stat() ½
Process spawn (vfork(), exec(), posix_spawn()
Threads (<pthread.h>)
<strings.h> ½
<locale.h>, lconv()

BSD

Feature Status
Safe string copying: strlcpy(), strlcat()
arc4random()

Common Extensions

Feature Status
#pragma once

GNU Extensions

GNU extensions are activated with the command-line argument -fgnu-extensions or with a -std=gnu* option.

When GNU extensions are enabled, some later version C features are available in earlier versions.

Compiler

Feature Status
alloca()
__attribute__
Statement expressions ✓
__asm__ name ✓
case ranges ✓
gnu89-style inline
Member designators using :
Computed gotos (&&label)
local (block scope) labels
__builtin_types_compatible_p()
__builtin_add_overflow() etc.
Nested functions
r-value array subscripts
void* arithmetic ✓
Cast to union
__extension__
128-bit integers
Half floats (_Float16 or __fp16)
Elvis operator (?:)
__builtin_apply(), constructed function calls
Dollar signs in identifiers ✓
__sync atomics

Preprocessor

Feature Status
, ## __VA_ARGS__ comma elision
__COUNTER__ ✓
__INCLUDE_LEVEL__
__INT_WIDTH__ and other <stdint.h> macros as builtins
Directives in macro arguments ✓
#include_next
GNU-style linemarkers

Clang Extensions

Clang extensions are included in GNU extensions. They are activated with the command-line argument -fgnu-extensions.

Feature Status
__has_warning
__has_extension
Deprecated, final, restricted expansion macros

Microsoft Extensions

Microsoft Visual C++ extensions (to C) are activated with the command-line argument -fms-extensions.

Feature Status
#pragma pack

Plan 9 Extensions

Plan 9 extensions are activated with the command-line argument -fplan9-extensions.

Feature Status
Anonymous non-inline struct
Implicit conversion of struct ptr to anonymous member ptr
Array designators without =

TinyCC Extensions

The only TinyCC extension Onramp plans to support is running as a script.

Feature Status
-run and #! script support