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I'm talking about clang-format, a formatting tool for C and C++ code, which has nothing to do with compiling your code with clang. You can use it with any compi

I'm talking about clang-format, a formatting tool for C and C++ code, which has nothing to do with compiling your code with clang. You can use it with any compiler. That said, the title is still a lie in that clang-format is not really at a fault here at all: clang-format triggered the issue on my codebase, by sorting header files, and this in turn triggered a libc performance issue. So as I initially say it, a commit which purely clang-format 'd my codebase caused a massive regression - but the full story is doesn't implicate clang-format at all, really.

glandium 7y ago
The title would be a /little/ clearer with a dash between Clang and format.
- ndesaulniers 7y ago
  Or "header inclusion order may affect performance." If someone points to this as a reason not to use clang-format...
- BeeOnRope 7y ago
  Good point, I put a hyphen a few places but not everywhere nor in the title. It seems hyphen is definitely the standard though. Fixed now [1], although the HN title will remain hyphen-free free I guess. --- [1] https://github.com/travisdowns/travisdowns.github.io/commit/95c6788e011eaa9638e12223d6d7dbd0465e5d8f https://github.com/travisdowns/travisdowns.github.io/commit/...
dleslie 7y ago
clang-format reordering includes is a terrible behaviour. It would break many C/C++ projects.
- glandium 7y ago
  It's optional, although it's enabled by default in the LLVM and Chromium styles.
  - dleslie 7y ago
    That's a bizarre optional feature to have; it's tantamount to having a "blindly reorder logic" function that sorts your source alphanumerically.
    - defap 7y ago
      Not really too bizarre. Header files should include or declare everything they need; they should not introduce include-order dependencies. Listing your includes in lexicographic order is a good way to enforce header completeness.
      - dleslie 7y ago
        It is by convention that C/C++ headers rely on preprocessor state to determine what blocks to reveal, macros to use, et al. It is quite common to have an auto-generated configuration header, for instance; or a precompiled header; or optional headers that, when present, mutate the behaviour of other headers. Every time you run a configure script for a C project there's a good chance you're interacting with code in this way.
        lorenzhs 7y ago
        Yeah, and if you want to use clang-format include reordering in such a project, you should read the docs for clang-format's "IncludeCategories". It allows you to separate your includes into blocks by providing regexes and associated priorities. Alphabetic sorting is done only within a block. It's not like clang-format was written by idiots who never used the language before. Maybe read up on what the tool actually does before you get all mad at them?
        dleslie 7y ago
        I'm not mad? I think it's a harmful anti-feature that's worthy of criticism.
        glandium 7y ago

glandium 7y ago

The title would be a /little/ clearer with a dash between Clang and format.

ndesaulniers 7y ago
Or "header inclusion order may affect performance." If someone points to this as a reason not to use clang-format...
BeeOnRope 7y ago
Good point, I put a hyphen a few places but not everywhere nor in the title. It seems hyphen is definitely the standard though. Fixed now [1], although the HN title will remain hyphen-free free I guess. --- [1] https://github.com/travisdowns/travisdowns.github.io/commit/95c6788e011eaa9638e12223d6d7dbd0465e5d8f https://github.com/travisdowns/travisdowns.github.io/commit/...

dleslie 7y ago

clang-format reordering includes is a terrible behaviour. It would break many C/C++ projects.

glandium 7y ago
It's optional, although it's enabled by default in the LLVM and Chromium styles.
- dleslie 7y ago
  That's a bizarre optional feature to have; it's tantamount to having a "blindly reorder logic" function that sorts your source alphanumerically.
  - defap 7y ago
    Not really too bizarre. Header files should include or declare everything they need; they should not introduce include-order dependencies. Listing your includes in lexicographic order is a good way to enforce header completeness.
    - dleslie 7y ago
      It is by convention that C/C++ headers rely on preprocessor state to determine what blocks to reveal, macros to use, et al. It is quite common to have an auto-generated configuration header, for instance; or a precompiled header; or optional headers that, when present, mutate the behaviour of other headers. Every time you run a configure script for a C project there's a good chance you're interacting with code in this way.
      - lorenzhs 7y ago
        Yeah, and if you want to use clang-format include reordering in such a project, you should read the docs for clang-format's "IncludeCategories". It allows you to separate your includes into blocks by providing regexes and associated priorities. Alphabetic sorting is done only within a block. It's not like clang-format was written by idiots who never used the language before. Maybe read up on what the tool actually does before you get all mad at them?
        dleslie 7y ago
        I'm not mad? I think it's a harmful anti-feature that's worthy of criticism.
      - glandium 7y ago