3 ms·

Maybe he is talking about exception safety. vector::push_back could throw an exception. But this is far fetched because people doing manual memory management d

Maybe he is talking about exception safety. vector::push_back could throw an exception. But this is far fetched because people doing manual memory management don't usually rely on exceptions, and just abort the program when this happens, so the leak is pointless.

jcelerier 4y ago
> But this is far fetched because people doing manual memory management don't usually rely on exceptions, I think you really, really underestimate the amount of codebases where a large part of the code is "normal" C++ with exceptions and someone does one specific module with manual malloc / free out of cargo-culting some RAII fears. Hell, even OP above talks about using vector along with their custom memory management scheme (which throws no matter if you use -fno-exceptions or not, as the actual "throw" call is in the precompiled libc++.so ; the code in <vector> just calls std::__throw_bad_array_new_length() indiscriminately : https://gcc.godbolt.org/z/fno8fYP7E https://gcc.godbolt.org/z/fno8fYP7E )
- flohofwoe 4y ago
  But with -fno-exceptions all exceptions cause a panic which stops execution of the program, right? So technically not a leak ;) (but TBH: exceptions don't even enter my mind anymore in the context of C++ because I had switched them off since I started C++ coding in the late 90's, I just don't see the value of exceptions in systems programming language, there's just too much compiler magic involved to make them work). I think the actual problem is that std::vector is doing its own memory management under the hood, which makes it hard to control what's going on from the outside. E.g. a design flaw of the C++ stdlib, not related to RAII.
  - jcelerier 4y ago
    > But with -fno-exceptions all exceptions cause a panic which stops execution of the program, right? plenty of cases where this isn't the case. -fno-exceptions just means that you want to not be able to throw for your own code. -fno-unwind-tables / -fno-asynchronous-unwind-tables makes your own code un-unwindable which is only safe if you are in entire control of the whole codebase, which is very rare in anything that is not simple games - no plug-in system, or any dynamic code loading or JIT'ing is safe as you don't know which user-provided function you call is going to throw. Likewise, you could be in the opposite case: imagine you're making a C++ plug-in for, say, 3DS Max, where error reporting is done through exceptions ; even if your own plug-in code is built with -fno-exceptions and does not itself throw at any point, you still want exceptions that may be coming from a 3DSMax function you called to propagate to your code back to the exception handler provided by 3DS Max - and for this RAII of your own types is needed if you don't want your own resources to be leaked.

jcelerier 4y ago

> But this is far fetched because people doing manual memory management don't usually rely on exceptions, I think you really, really underestimate the amount of codebases where a large part of the code is "normal" C++ with exceptions and someone does one specific module with manual malloc / free out of cargo-culting some RAII fears. Hell, even OP above talks about using vector along with their custom memory management scheme (which throws no matter if you use -fno-exceptions or not, as the actual "throw" call is in the precompiled libc++.so ; the code in <vector> just calls std::__throw_bad_array_new_length() indiscriminately : https://gcc.godbolt.org/z/fno8fYP7E https://gcc.godbolt.org/z/fno8fYP7E )

flohofwoe 4y ago
But with -fno-exceptions all exceptions cause a panic which stops execution of the program, right? So technically not a leak ;) (but TBH: exceptions don't even enter my mind anymore in the context of C++ because I had switched them off since I started C++ coding in the late 90's, I just don't see the value of exceptions in systems programming language, there's just too much compiler magic involved to make them work). I think the actual problem is that std::vector is doing its own memory management under the hood, which makes it hard to control what's going on from the outside. E.g. a design flaw of the C++ stdlib, not related to RAII.
- jcelerier 4y ago
  > But with -fno-exceptions all exceptions cause a panic which stops execution of the program, right? plenty of cases where this isn't the case. -fno-exceptions just means that you want to not be able to throw for your own code. -fno-unwind-tables / -fno-asynchronous-unwind-tables makes your own code un-unwindable which is only safe if you are in entire control of the whole codebase, which is very rare in anything that is not simple games - no plug-in system, or any dynamic code loading or JIT'ing is safe as you don't know which user-provided function you call is going to throw. Likewise, you could be in the opposite case: imagine you're making a C++ plug-in for, say, 3DS Max, where error reporting is done through exceptions ; even if your own plug-in code is built with -fno-exceptions and does not itself throw at any point, you still want exceptions that may be coming from a 3DSMax function you called to propagate to your code back to the exception handler provided by 3DS Max - and for this RAII of your own types is needed if you don't want your own resources to be leaked.