问题描述
此指出，
这是否意味着尝试
TL; DR NO ，与错误代码处理相比，异常通常比非特殊路径更快。
嗯，明显的说法是比较什么？
与不处理错误相比，显然降低了性能;但性能是否缺乏正确性？我会认为它不是，所以让我们假设你的意思是与一个 c $ c>如果表示他们最终具有相同的成本（或略高）。
在C ++中，所有主要的编译器（gcc在4.x系列中引入了它，MSVC将其用于64位代码）现在使用零成本异常模型。如果您阅读了关于Need4Sleep的，它被列为表驱动的方法。这个想法是，对于程序的每个点，可能会抛出您在一个边表中注册一些位和块，这将允许您找到正确的catch子句。老实说，与旧的策略相比，它的执行速度比较复杂，但是，零成本名称是由于免费的事实是不会引起异常的。对比一下CPU上的分支错误预测。另一方面，当抛出异常时，惩罚是巨大的，因为表存储在冷区中（因此可能需要往返RAM或更差）...但异常总结一下，现代C ++编译器的异常比错误代码要快，代价较大的二进制（由于静态表）。
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This link states,
Does it mean that having a try block reduces performance due to the extra task of "inspection" during run time?
TL;DR NO, exceptions are usually faster on the non-exceptional path compared to error code handling.
Well, the obvious remark is compared to what ?
Compared to not handling the error, it obviously decrease performance; but is performance worth the lack of correctness ? I would argue it is not, so let us supposed that you meant compared to an error code checked with an if statement.
In this case, it depends. There are multiple mechanisms used to implement exceptions. Actually, they can be implemented with a mechanism so close to an if statement that they end up having the same cost (or slightly higher).
In C++ though, all major compilers (gcc introduced it in 4.x serie, MSVC uses it for 64 bits code) now use the Zero-Cost Exception Model. If you read this technical paper that Need4Sleep linked to, it is listed as the table-driven approach. The idea is that for each point of the program that may throw you register in a side-table some bits and pieces that will allow you to find the right catch clause. Honestly, it is a tad more complicated implementation-wise than the older strategies, however the Zero Cost name is derived by the fact that it is free should no exception be thrown. Contrast this to a branch misprediction on a CPU. On the other hand, when an exception is thrown, then the penalty is huge because the table is stored in a cold zone (so likely requires a round-trip to RAM or worse)... but exceptions are exceptional, right ?
To sum up, with modern C++ compilers exceptions are faster than error codes, at the cost of larger binaries (due to the static tables).
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