[llvm-dev] LLVM coding standards and order of includes

Martin J. O'Riordan via llvm-dev
2015-09-10T16:00:05Z

Generally it is safer to include ISO headers first (using the ‘#include
<...>’ form) so as to minimise the possibility that a later user
declaration or macro definition interferes with the correctness of the Standard
libraries.  It also tends to make pre-compiled header implementations faster and
more shareable across a larger set of files.



I would like to suggest revising the LLVM coding standard to place the “System
#includes” first.



            MartinO



From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of David
Blaikie via llvm-dev
Sent: 10 September 2015 16:33
To: Russell Wallace <russell.wallace at gmail.com>
Cc: llvm-dev <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] LLVM coding standards and order of includes







On Thu, Sep 10, 2015 at 8:06 AM, Russell Wallace via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org> > wrote:

According to the LLVM coding standards,



Immediately after the
<http://llvm.org/docs/CodingStandards.html#header-file-comment> header
file comment (and include guards if working on a header file), the
<http://llvm.org/docs/CodingStandards.html#minimal-list-of-includes>
minimal list of #includesrequired by the file should be listed. We prefer these
#includes to be listed in this order:

1.	Main Module Header
2.	Local/Private Headers
3.	llvm/...
4.	System #includes

If a program is using LLVM, and also using a third-party library such as GMP,
where would the coding standard have the GMP include be placed relative to the
above order?


The LLVM coding conventions are really intended for LLVM's code itself, they
probably don't cover many situations that would arise when using LLVM code
in broader applications like this... (nor is it likely we'd want to add
wording to the style guide to clarify those use cases, unfortunately).

That said, we do have one (zlib compression?) or two (maybe md5 too?) external
libraries used in LLVM, I imagine they get bundled in with the system includes,
but I've not looked (& given that there aren't many, they might not
be done in any consistent/deliberate manner)

- Dave

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