Question: Where does the #include " " conding convention come from?

[kfessel]

Where does the #include coding convention come from?

Description

RIOT-OS has a coding convention of using #include " " for its RIOT System includes to differentiate them from #include < > which should be used for compiler includes only.

This seems special to me and at least to some other people PR in ndn-riot I tried to find the reasoning in the RIOT git history but i failed. In 7caf788 (14/11/2013) Ludwig Ortmann mentioned the coding convetion (maybe the first time). The Coding_Convetions .md file got added by @maribu at 25/10/2019 but somehow must have been there before.

As i wrote in the ndn PR at least Arduino and Zephy use < > for non compiler library includes.

Useful links

a blog post that did some digging through c standard
not very help full gcc manual
microsoft was a little more clear there are some words about parent includes that if they apply to gcc my lead to some difficult to explain behavior.

K&R 2 page 102 and 103

my 2 cent

Reading the blog-post mentioned above i get the C-Standard does not say anything to distinguish #include "" from #include <> (i also checked if newer or newer standards say something but the paragraph seems to be unchanged); K&R said something which the RIOT CC conflicts with.

quoting myself from the ndn PR:

K&R could have saved us from this discussion if they just had not defined the fallback case for " "

it would have been you know the path -> " "
compiler has to search -> < >

the fallback case for " " is what RIOT is using

[kaspar030]

Where does the #include coding convention come from?

Style. "foo.h" is "one of ours", whereas <foo.h> is "comes from the runtime/libc/whatever". That only goes upstream, we consider package headers as "ours".
The angle brackets form searches "preconfigured list of standard system directories". For RIOT being a library OS usually compiled to a baremetal target, that means toolchain provided include paths. Quote includes search paths added with -I before those. So using the quote form hints to the reader that "we don't expect this to be found in the toolchain include paths".

[miri64]

The Coding_Convetions .md file got added by @maribu at 25/10/2019 but somehow must have been there before.

For reference, as the PR importing that .md indicates: the coding conventions where maintained in the Wiki before. Best way to track the history there is to check out the wiki via git (git clone [email protected]:RIOT-OS/RIOT.wiki.git and view the log of the Coding-conventions.md) there.

[kfessel]

i just checked gcc does not apply what msvc does for the quoted form rule 2 (the parrent include) < this would be a problem
incl_test.zip

cd main
gcc -I ../inc1 -I ../inc2 main.c 

gcc for quoted -> the currents file directory -> the rest is like angel brackets
gcc for angel -> search -I include paths last added is first to be searched -> search compiler system includes

the <> form also searches -I first before compiler

[stale]

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[kfessel]

... So using the quote form hints to the reader that "we don't expect this to be found in the toolchain include paths".

Most other projects use #include " " to indicate that the file is found right next to the file including and < > to indicat it is in the include path (not caring if it is in the libc or in (lib))

[maribu]

Question was answered --> closing this.