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LCA: Lessons from 30 years of SendmailLCA: Lessons from 30 years of SendmailPosted Feb 11, 2011 9:33 UTC (Fri) by cmccabe (guest, #60281)In reply to: LCA: Lessons from 30 years of Sendmail by nix Parent article: LCA: Lessons from 30 years of Sendmail
See my comment below. Basically, private data members of a class also need to be #included in that class' header file. So you *cannot* "avoid parsing the vast majority of headers more than once."
Under ideal conditions, C++ compilation is slow. If you add even a few non-ideal conditions, like programmers who love to define functions in header files "for performance", extensive use of templates, auto-generated anything, or unecessary cross-module dependencies, it becomes positively glacial.
Unfortunately real-world projects tend to have some or all of these conditions. I'm too lazy to find the reference now, but Google's C++ compile times are said to be measured in hours. And those guys read Effective C++ and know their stuff.
Precompiled headers sound helpful, but only for headers you are including from external libraries. Maybe they would be useful for something like QT? I haven't used precompiled headers.
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LCA: Lessons from 30 years of Sendmail Posted Feb 19, 2011 0:24 UTC (Sat) by nix (subscriber, #2304) [Link]
Er, when I said 'more than once' I said 'more than once per translation unit', and this is almost universal. This reduces your claimed O(n^2) to, uh, O(nm) where n is the number of translation units and m is the number of headers.
Precompiled headers are useful in any project where you have one great big header that #includes a lot of stuff. This is extremely common.
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