That’s my guess, but there was a conversation on the mailing list a few months ago that wasn’t just immediately shut down, even by other prolific developers
Ts’o seems skeptical, but is at least asking whether c++ has improved
Take a look at what even the proposer is saying wouldn’t be allowed in:
(1) newand delete. There's no way to pass GFP_* flags in.
(2) Constructors and destructors. Nests of implicit code makes the code less
obvious, and the replacement ofstatic initialisation with constructor
calls would make the code size larger.
(3) Exceptions and RTTI. RTTI would bulk the kernel up too much and
exception handling is limited without it, and since destructors are not
allowed, you still have to manually clean up after an error.
(4) Operator overloading (except in special cases).
(5) Function overloading (except in special inline cases).
(6) STL (though some type trait bits are needed to replace __builtins that
don't exist in g++).
(7) 'class', 'private', 'namespace'.
(8) 'virtual'. Don't want virtual base classes, though virtual function
tables might make operations tables more efficient.
C++ without class, constructors, destructors, most overloading and the STL? Wow.
I’ve only worked on a few embedded systems where C++ was even an option, but they allowed 2, 4, 5, and 7. Though, for the most part most classes were simple interfaces to some sort of SPI/I2C/CAN/EtherCAT device, most of which were singletons.
That’s my guess, but there was a conversation on the mailing list a few months ago that wasn’t just immediately shut down, even by other prolific developers
Ts’o seems skeptical, but is at least asking whether c++ has improved
https://lore.kernel.org/lkml/20240110175755.GC1006537@mit.edu/
Take a look at what even the proposer is saying wouldn’t be allowed in:
(1) new and delete. There's no way to pass GFP_* flags in. (2) Constructors and destructors. Nests of implicit code makes the code less obvious, and the replacement of static initialisation with constructor calls would make the code size larger. (3) Exceptions and RTTI. RTTI would bulk the kernel up too much and exception handling is limited without it, and since destructors are not allowed, you still have to manually clean up after an error. (4) Operator overloading (except in special cases). (5) Function overloading (except in special inline cases). (6) STL (though some type trait bits are needed to replace __builtins that don't exist in g++). (7) 'class', 'private', 'namespace'. (8) 'virtual'. Don't want virtual base classes, though virtual function tables might make operations tables more efficient.C++ without
class, constructors, destructors, most overloading and the STL? Wow.That doesn’t really surprise me, as most of those are the same requirements from any embedded development use case using c++ that I’ve worked on
4 and 5 are the only ones stricter than I’m used to
I’ve only worked on a few embedded systems where C++ was even an option, but they allowed 2, 4, 5, and 7. Though, for the most part most classes were simple interfaces to some sort of SPI/I2C/CAN/EtherCAT device, most of which were singletons.