compatibility.md

Toolchain compatibility

Policy

C-Next's toolchain requirements are per-feature, not global.

The baseline is C99 (C++11 with --cpp), and code that uses none of the features below really does compile with any conforming compiler. Each feature listed here adds a requirement only to files that use it: you pay for CMSIS only if you write a critical section, and for C11 only if you index the bits of a float.

This file is generated from the transpiler's own requirements registry, so it cannot fall out of step with what the code generator emits. To see what your project needs -- as opposed to what C-Next might need -- transpile it: the requirements are reported at the end of the run.

Baseline

transpile mode	language standard	compiler	platform library
C (default)	C99	any conforming	none
C++ (--cpp)	C++11	any conforming	none

Conditional requirements

feature	you pay it when	mode	language standard	compiler	platform library	emitted
float bit indexing	reading or writing a bit range of an f32 or f64	c	C11	any conforming	none	_Static_assert
float bit indexing	reading or writing a bit range of an f32 or f64 with --cpp	cpp	C++11	any conforming	none	static_assert
interrupt masking	a critical block, or an atomic read-modify-write on a target without LDREX/STREX, and defined(__arm__) || defined(__ARM_ARCH)	c, cpp	C99	GNU inline assembly, __attribute__((always_inline))	ARMv7-M core	__asm volatile ("MRS %0, primask"), __attribute__((always_inline))
interrupt masking	a critical block, or an atomic read-modify-write on a target without LDREX/STREX, and defined(__arm__) && defined(ARDUINO)	c, cpp	C99	GNU inline assembly, __attribute__((always_inline))	ARMv7-M core + Arduino core	noInterrupts()
interrupt masking	a critical block, or an atomic read-modify-write on a target without LDREX/STREX, and defined(__AVR__)	c, cpp	C99	any conforming	avr-libc	SREG, cli()
interrupt masking	a critical block, or an atomic read-modify-write on a target without LDREX/STREX, and neither ARM nor AVR	c, cpp	C99	any conforming	CMSIS	__disable_irq(), __get_PRIMASK(), __set_PRIMASK()
atomic read-modify-write	compound assignment to an atomic variable on a target with LDREX/STREX	c, cpp	C99	any conforming	CMSIS + ARMv7-M	__LDREXB/H/W, __STREXB/H/W
struct initializer	initializing a struct in --cpp mode	cpp	C++20	designated initializers in C++	none	.field = value inside a braced initializer
struct initializer	a non-declaration struct literal in --cpp mode	cpp	C++11	compound literals in C++	none	(T){ ... } in C++
overflow panic (--debug)	transpiling with --debug and using a clamp type	c, cpp	C99	any conforming	hosted libc	fprintf(stderr, ...), abort()

Compiler version floors

None. No construct C-Next emits has a minimum compiler version.

C-Next previously required GCC 5+ / Clang 3.8+ wherever an unsigned clamp helper was emitted, because those helpers called __builtin_add_overflow and friends. Those calls were unreachable -- the preceding range check is already a complete overflow test -- and were removed in #1143.

Compiler extensions

These are not standard C or C++. GCC and Clang accept them; IAR, TI CGT, Keil and MSVC may not.

extension	used by	emitted
GNU inline assembly, __attribute__((always_inline))	interrupt masking	__asm volatile ("MRS %0, primask"), __attribute__((always_inline))
GNU inline assembly, __attribute__((always_inline))	interrupt masking	noInterrupts()
designated initializers in C++	struct initializer	.field = value inside a braced initializer
compound literals in C++	struct initializer	(T){ ... } in C++

Platform libraries

library	feature	selected when	emitted
ARMv7-M core	interrupt masking	defined(__arm__) || defined(__ARM_ARCH)	__asm volatile ("MRS %0, primask"), __attribute__((always_inline))
ARMv7-M core + Arduino core	interrupt masking	defined(__arm__) && defined(ARDUINO)	noInterrupts()
avr-libc	interrupt masking	defined(__AVR__)	SREG, cli()
CMSIS	interrupt masking	neither ARM nor AVR	__disable_irq(), __get_PRIMASK(), __set_PRIMASK()
CMSIS + ARMv7-M	atomic read-modify-write	always	__LDREXB/H/W, __STREXB/H/W
hosted libc	overflow panic (--debug)	always	fprintf(stderr, ...), abort()

MISRA C:2012 guidelines affected

See misra-compliance.md for the full assessment.

guideline	features that bear on it
1.1	baseline, float bit indexing
1.2	interrupt masking, struct initializer
20.8	interrupt masking
20.9	interrupt masking
20.14	interrupt masking
21.6	overflow panic (--debug)
21.8	overflow panic (--debug)
Dir 4.3	interrupt masking
Dir 4.9	interrupt masking, atomic read-modify-write