Regarding prefixes, I advice that you start by writing the library in C and then wrap it in C++ for a variety of reasons that you might want to consider. In C++ you should indeed always use namespace.
Header guards have the advantage over pragma once that they are standard and you can also use them to check if a library is included. I might remove that since maybe it's not that important and people might different views.
Regarding constants, I was referring to things such as numeric constants for which you would constexpr in C++. Maybe I can be more explicit there. Thanks for the feedback.
It’s very hard to write correct C code which does IO and supports multithreading. Take a look at Microsoft’s implementation of fprintf, copy-pasted from Windows 10 SDK: https://gist.github.com/Const-me/f1bb320969adde6c79694265ea6... They use RAII to set & revert the locale, and to lock RAM buffer to avoid corruption by another threads. They use C++ lambda for exception handling. They even use C++ template to avoid code duplication between printf and wprintf.
But these C++ shenanigans are not exposed to user, user calls their `printf` (possibly in a code built by C compiler) and it just works.
This is just a random unsubstantiated statement. There's nothing particularly "hard" about writing IO libraries that is language-specific. Multithreaded or not.
The hard part is making sure you release stuff every time you acquire stuff, exactly once. C++ RAII makes it almost trivially simple, but standard C has nothing comparable. When you only targeting gcc and clang can use __attribute__(cleanup) in C, it helps but still it’s more limited and more error prone compared to destructors.
Oy vey... you can't be serious. That's rudimentary basics of using any API.
There’re also other programs in wide use, which need to reliably work for hours, sometimes weeks. Some of them have huge amount of code they built from, written by many people over many years. Combine that with large enough APIs (some peripheral devices have hundreds of writeable registers of state; or D3D11 exposes huge amount of very complicated state, only limited by VRAM amount which is measured in gigabytes) and it’s very easy to make bugs in such programs.
Leaks of memory, handles, sockets, and many other resource types e.g. GPU ones. Deadlocks caused by locked mutexes, or threads which exit but forgot to release something they needed to release. Unwanted changes to global or thread state, both internal to the process and external (locales, formatting options, console colors, process and thread priorities, current directory, environment variables, CPU registers like FPU flags and interrupt masks, GPU render states) caused by some code changing stuff but not reverting the changes back. Unwanted state changes of custom peripheral devices, due to the same reason.
C++ RAII is not a silver bullet, but it does help a lot for all these things.
If you need to rely on RAII in order not to screw things up, then it's an issue with the coding style or the application design. That's what needs fixing. Not the language choice. You got it backwards.
The problem is only tangentially related to API semantics. The problem is mutating state. The state is not necessarily managed by an API, for instance CPU registers aren’t, you modify them directly. Same with other global state like I/O formatting options and locales, these things are just global variables.
C is a perfectly fine language for tasks of all kinds. The fact that it expects programmers to take greater care when using it is not a reason enough to dismiss it as a general-purpose language. Not everyone needs (or wants) to ride a tricycle wearing knee pads and a helmet to get from A to B.
The reason is very simple, the billions of wasted money fixing security exploits caused by industry's adoption of C.
Morris worm is more than 30 years old, and the old ways can still be used to attack modern systems that people insist in writing using C.
https://msrc-blog.microsoft.com/2019/06/14/prevent-the-impac...
https://support.apple.com/en-us/HT210348
https://msrc-blog.microsoft.com/2019/07/16/a-proactive-appro...
https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Pr...
https://security.googleblog.com/2019/08/adopting-arm-memory-...
Even in 2019, the C ABI is the one universally agreed-upon cross-language ABI for languages compiled to native code.
However given that at least C++ does support ways to tame C, after all the whole purpose was for Bjarne never to repeat his Simula into BCPL rewrite experience ever again, it is up for security conscious to decide what legacy they want to leave, when the option is between both those languages.
On the other hand maybe C should be used to write Skynet, so that we stand a chance.
C ABI happens to be the mixed up with OS ABI, on OS written in C like UNIX clones, on mainframes, and other competing OSes that isn't the case, because they use other systems languages on their stack, or even some kind of bytecode based interoperability format.
However since the context here is game libraries, C ABI == OS ABI pretty much applies everywhere (except WebAssembly or Android JNI) and lets leave at there.
Since C++98, writing a library in C++, even if exposing it as extern "C", provides the following benefits for the quality of code implementation:
- less implicit conversions
- use of reference types instead of pointers for memory accesses we can be sure are never allowed to be null
- use of namespaces instead of Assembly style programming of having to come up with prefixes for code organization
- bounds checking for strings, vectors and other related data structures provided one uses the library types. They can even be left turned on for release mode, if the profiler shows there is no visible impact on hot paths
- use of RAII to manage library internal state and reduce leak occurrences
- ISO C++ working group is actually striving for reducing the amount of UB from its 200+ use cases, unlike ISO C group
- strong typed enums introduced in C++11 don't have implicit conversions and must map to their underlying types
- type safe compile time code execution, specially helpful in games, used for stuff like generating trigonometry tables
- templates as replacement for pre-processor magic that eventually goes subtly wrong when the #include order gets misplaced or too few parenthesis are used
If this still sounds absurd, well all major C compilers are now implemented in C++, Microsoft rewrote their C standard library in C++ with extern "C" entry points, Android NDK is actually implemented in a mix of C++ and Java (via JNI) also using extern "C" calls.
I did, in my first comment.
C++ namespaces lead to much more readable code, compared to these prefixed names.
C++/11 scoped enums eliminate a class of bugs: when you have many different constants on the API surface, multiple functions accepting them, and erroneously use the constant of a wrong function. Example:
enum Lod { Low, High };
enum SomethingElse { Other };
void setLoD( enum Lod v );
void bug()
{
setLoD( Other );
}— Every language out there has a way to call into C
— If your code is slower than C, someone will rewrite it in C.
— If your library is written in C it means it can be used on any OS, console or mobile device and even on the web.
— Not everyone wants to use C++ (some prefer C).
— It is easier in general for a C++ user to use a C library than it is for a C user to use a C++ library.
— C++ is not as easy to write wrappers for in other languages.
— Unless you limit which C++ features you use (to the point where you are pretty much left with C) a lot of people won’t be able to use your library.
PS. If your original comment had been phrased the way you put it here I might have made the same comment, but I would not have downvoted it. Here, you’re at least providing some supporting evidence for your assertions which makes it a much more valuable contribution to the conversation.
When used correctly, C++ is not slower than C. Sometimes faster, a classic example is C qsort versus std::sort.
> If your library is written in C it means it can be used on any OS, console or mobile device and even on the web.
C++ is good in that regard. I know only 1 mainstream platform where C++ adds significant friction compared to C, that’s iOS, because their objective C is a superset of C. The rest of them (Windows, Linux including embedded, game consoles, android) support C++ just fine.
> Not everyone wants to use C++ (some prefer C).
Most people are OK with C++, especially in the context of game development.
> to the point where you are pretty much left with C
No, not with C. Namespaces and scoped enums are awesome.
Another thing, inside the implementation of the library, you can use whatever C++ language features you please, even the features that would be inappropriate when exposed at the API surface of the library. For example, MS implemented parts of their C runtime library with C++ classes, RAII, lambdas and templates, eliminating duplicated code for char/wchar_t routines. Obviously, you don’t need C++ to consume that library, just C is enough, but it’s implemented in modern C++. On my system, that source is in "C:\Program Files (x86)\Windows Kits\10\Source\10.0.18362.0\ucrt\stdio\output.cpp".
Apple’s compiler supports overlaying Objective-C features on top of C++ instead of C; it’s called Objective-C++.
Then I’ve got an e-mail from a developer who asked a few things how to back port my changes to C. I answered their questions, but I was curious why. They replied it’s because Objective C and iOS. Personally, I haven’t been developing for iOS for several years, but I don’t think people would do such things for lulz.
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-1193...
Other than that, I'm not surprised the file in question is C. Even ignoring the fact that it was you to get the link. And even ignoring that it's about a security problem...
Other than that, from a user perspective, software written in C is among the most reliable software I'm using. I'm looking at Linux, vim, xterm and so much of the infrastructure that I don't even know by name.
Some people value "security" more than they value the beauty of a nice, a maintainable, or a practical program. That's ok as far as I'm concerned...
https://msrc-blog.microsoft.com/2019/06/14/prevent-the-impac...
https://security.googleblog.com/2019/08/adopting-arm-memory-...
https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Pr...
Seatbelts and helmets are also a nuisance, maybe we should get rid of them, that is my perspective.
They are not random, only to those that don't care about improving the quality of our eco-system.
Software liability couldn't come soon enough.
I've never understood what's the practical difference between NS::foo() and NS_foo() with regards to preventing name collisions. Can someone enlighten me?
I know some disadvantages of the namespacing variant, though. There are now multiple names for the items defined in the namespace: the qualified one and the unqualified one. The latter is often not unique in practice, since the programmer relies on the qualified name for uniqueness. In effect, making simple text searches for identifiers is very unreliable. Note I do use IDEs, but I also code in vim, and I need to do simple text searches even when working in Visual Studio.
Additionally, there's no guarantee that there are no spaces around the scoper. I believe "NS :: foo" is just as valid, which makes me uneasy with regards to text search, as well.
Another issue I have:
$ cat test.cpp
namespace NS { int foo() { return 0; } };
$ g++ -c -o test.o test.cpp
$ nm test.o
0000000000000000 T _ZN2NS3fooEv # I hate my life
I haven't found those working for me. Apart from the namespacing issue described above, I have issues with explicit enum types. One issue is that I often need to put sentinel / "missing" values (typically the value is -1) where an enum value is expected. Even more often, I want to iterate over the values of an enum. C++'s enum "type safety" makes working like this really unergonomic.
The way I go about this is I don't even use names for my enum types, and I fully qualify the enumeration values.
enum {
FPGAPARAM_BLA,
FPGAPARAM_BLUB,
FPGAPARAM_FOO,
NUM_FPGAPARAM_KINDS
};
struct ASDF {
int fpgaparamKind; // obvious what kind of values are expected here...
};
for (int i = 0; i < NUM_FPGAPARAM_KINDS; i++) {
struct ASDF asdf;
asdf.fpgaParamKind = i;
do_asdf(&asdf);
}
They both do the job. There’re 2 practical differences.
1. You can write `using namespace` inside functions or the whole .cpp files. This often makes the consuming code more readable.
2. Sometimes you want to replace implementations. With prefixes it gonna be massive changes likely to introduce new bugs. With namespaces, replace `using std::vector` with `using eastl::vector` and you’re done.
> Even more often, I want to iterate over the values of an enum.
I only need to do that rarely. When I do, I cast types like this:
enum struct eParamKind : uint8_t
{
Bla, Blub, Foo, valuesCount
};
for( uint8_t i = 0; i < (uint8_t)eParamKind::valuesCount; i++ )
{
const eParamKind pk = (eParamKind)i;
// Whatever
}
I disagree on ergonomics. VS makes much easier to consume API with strongly typed enums: ePar<Ctrl+Space>::f<Enter>, to type eParamKind::Foo It’s similar with namespaces versus prefixes BTW, IDE will first auto-complete the namespace, then only list members of that namespace once you type the `::`
Update: another C++ feature relevant for game development is overloaded operators. Games often do non-trivial amount of math on small vectors, matrices and quaternions. Overloaded operators make sense for them.
> replace `using std::vector` with `using eastl::vector` and you’re done.
The pipe dream of reusability.. If I ever happen to be in a situation where that will work, I'll happily use a text replace to change my identifiers. Or just link a different library if it has the same names.
It doesn’t on my PC.
I’ve copy-pasted C enum from your example, when I type FPG<Ctrl+Space> there’s no way to auto-complete just the FPGAPARAM_ part, to be able to then press F to get FPGAPARAM_FOO. Using VC2017 here, with latest Visual Assist.
Which C++ IDE are you using?
> The pipe dream of reusability.
Did it more than once.
Here’s one open source project where I’ve replaced most parts of the C++ standard library with EASTL: https://github.com/Const-me/vis_avs_dx
Here’s my header-only C++ library which allows users to switch between 16-bytes/32-bytes wide SIMD by using different C++ namespace, either Intrinsics::Sse or Intrinsics::Avx: https://github.com/Const-me/IntelIntrinsics/
C++ defines don’t respect namespaces so you are pretty much screwed in anycase.
BTW, you can disable these windows.h macros by defining NOMINMAX. I usually do, because I prefer min/max from <algorithm>; in some edge cases std::min / std::max can be twice as fast because compiler guarantees to compute arguments exactly once.
> Always prefix your names to avoid name collisions
Solved by C++ namespaces.
> Use header guards instead of #pragma once.
#pragma once is supported by all mayor compilers, header guards can introduce bugs, also #pragma once builds measurably faster: https://github.com/electronicarts/EASTL/blob/3.15.00/include...
> Expose constants to the user using constexpr variables.
Modern C++ has strongly-typed scoped enums for such constants.