我能想到有两个问题可能会影响c++程序的编译速度。

POSSIBLE ISSUE #1 - COMPILING THE HEADER: (This may or may not have already been addressed by another answer or comment.) Microsoft Visual C++ (A.K.A. VC++) supports precompiled headers, which I highly recommend. When you create a new project and select the type of program you are making, a setup wizard window should appear on your screen. If you hit the “Next >” button at the bottom of it, the window will take you to a page that has several lists of features; make sure that the box next to the “Precompiled header” option is checked. (NOTE: This has been my experience with Win32 console applications in C++, but this may not be the case with all kinds of programs in C++.)

POSSIBLE ISSUE #2 - THE LOCATION BEING COMPILED TO: This summer, I took a programming course, and we had to store all of our projects on 8GB flash drives, as the computers in the lab we were using got wiped every night at midnight, which would have erased all of our work. If you are compiling to an external storage device for the sake of portability/security/etc., it can take a very long time (even with the precompiled headers that I mentioned above) for your program to compile, especially if it’s a fairly large program. My advice for you in this case would be to create and compile programs on the hard drive of the computer you’re using, and whenever you want/need to stop working on your project(s) for whatever reason, transfer them to your external storage device, and then click the “Safely Remove Hardware and Eject Media” icon, which should appear as a small flash drive behind a little green circle with a white check mark on it, to disconnect it.

我希望这对你有帮助;如果有，请告诉我!：）

几个原因

头文件

每个编译单元都需要(1)加载和(2)编译数百甚至数千个头文件。 每个编译单元通常都需要重新编译它们， 因为预处理器确保编译头文件的结果可能在每个编译单元之间有所不同。 (宏可以在一个编译单元中定义，它会改变头文件的内容)。

这可能是主要原因，因为它需要为每个编译单元编译大量的代码， 此外，每个头文件都必须编译多次 (对于包含它的每个编译单元一次)。

链接

一旦编译完成，所有的目标文件都必须链接在一起。 这基本上是一个整体过程，不能很好地并行化，并且必须处理您的整个项目。

解析

语法非常复杂，难以解析，严重依赖上下文，并且很难消除歧义。 这要花很多时间。

模板

在c#中，List<T>是唯一被编译的类型，无论程序中有多少个List实例化。 在c++中，vector<int>和vector<float>是一个完全独立的类型，它们必须分别编译。

Add to this that templates make up a full Turing-complete "sub-language" that the compiler has to interpret, and this can become ridiculously complicated. Even relatively simple template metaprogramming code can define recursive templates that create dozens and dozens of template instantiations. Templates may also result in extremely complex types, with ridiculously long names, adding a lot of extra work to the linker. (It has to compare a lot of symbol names, and if these names can grow into many thousand characters, that can become fairly expensive).

当然，它们加剧了头文件的问题，因为模板通常必须在头文件中定义， 这意味着必须为每个编译单元解析和编译更多的代码。 在纯C代码中，标头通常只包含前向声明，但实际代码很少。 在c++中，几乎所有的代码都驻留在头文件中是很常见的。

优化

c++允许进行一些非常戏剧化的优化。 c#或Java不允许完全消除类(为了反射的目的，它们必须存在)， 但即使是一个简单的c++模板元程序也可以很容易地生成几十个或数百个类， 所有这些都在优化阶段被内联并再次消除。

此外，c++程序必须由编译器完全优化。 c#程序可以依赖JIT编译器在加载时执行额外的优化， c++没有任何这样的“第二次机会”。编译器生成的是它将要得到的优化。

机

c++被编译成机器代码，这可能比Java或. net使用的字节码更复杂(特别是在x86的情况下)。 (这只是出于完整性而提到的，因为它是在评论中提到的。 在实践中，这一步所花费的时间不太可能超过编译时间的一小部分)。

结论

这些因素中的大多数是由C代码共享的，这实际上是相当有效的编译。 在c++中，解析步骤要复杂得多，可能会占用更多的时间，但主要的问题可能是模板。 它们很有用，并使c++成为一种更强大的语言，但它们也在编译速度方面付出了代价。

c++被编译成机器代码。所以你有预处理器，编译器，优化器，最后是汇编器，所有这些都必须运行。

Java和c#被编译成字节码/IL, Java虚拟机/。NET框架执行(或JIT编译成机器代码)之前执行。

Python是一种解释型语言，它也被编译成字节码。

我相信还有其他原因，但总的来说，不需要编译为本机机器语言可以节省时间。

另一个原因是使用C预处理器来定位声明。即使使用了头保护，.h仍然必须在每次包含它们时被反复解析。一些编译器支持预编译的头文件，可以帮助解决这个问题，但它们并不总是被使用。

参见:c++常见问题答案

在大型c++项目中减少编译时间的一个简单方法是创建一个包含项目中所有cpp文件的*.cpp包含文件并编译该文件。这将头爆炸问题减少到一次。这样做的好处是，编译错误仍然会引用正确的文件。

例如，假设你有a.cpp, b.cpp和c.cpp。创建一个文件:everything.cpp:

#include "a.cpp"
#include "b.cpp"
#include "c.cpp"

然后通过将everything.cpp编译项目

我能想到有两个问题可能会影响c++程序的编译速度。

POSSIBLE ISSUE #1 - COMPILING THE HEADER: (This may or may not have already been addressed by another answer or comment.) Microsoft Visual C++ (A.K.A. VC++) supports precompiled headers, which I highly recommend. When you create a new project and select the type of program you are making, a setup wizard window should appear on your screen. If you hit the “Next >” button at the bottom of it, the window will take you to a page that has several lists of features; make sure that the box next to the “Precompiled header” option is checked. (NOTE: This has been my experience with Win32 console applications in C++, but this may not be the case with all kinds of programs in C++.)

POSSIBLE ISSUE #2 - THE LOCATION BEING COMPILED TO: This summer, I took a programming course, and we had to store all of our projects on 8GB flash drives, as the computers in the lab we were using got wiped every night at midnight, which would have erased all of our work. If you are compiling to an external storage device for the sake of portability/security/etc., it can take a very long time (even with the precompiled headers that I mentioned above) for your program to compile, especially if it’s a fairly large program. My advice for you in this case would be to create and compile programs on the hard drive of the computer you’re using, and whenever you want/need to stop working on your project(s) for whatever reason, transfer them to your external storage device, and then click the “Safely Remove Hardware and Eject Media” icon, which should appear as a small flash drive behind a little green circle with a white check mark on it, to disconnect it.

我希望这对你有帮助;如果有，请告诉我!：）