[libvirt] [PATCH 2/3] docs: hacking: Add good practices for shortening conditional expressions

[Martin Kletzander]

On Thu, May 09, 2019 at 12:43:33PM +0200, Peter Krempa wrote:
>Document that checking if a integer is (non-)zero should (not must)
>avoid the shortened form that C allows as it may confuse readers into
>overlooking the other possible values which might be interresting to
>handle.
>
>While pointers have distinct values from the point of view of the code
>we only care whether it's non-NULL and thus it's documented it's okay
>to shorten those.
>
>Signed-off-by: Peter Krempa <pkrempa at redhat.com>
>---
> docs/hacking.html.in | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
>diff --git a/docs/hacking.html.in b/docs/hacking.html.in
>index 081d793360..a2800853ef 100644
>--- a/docs/hacking.html.in
>+++ b/docs/hacking.html.in
>@@ -826,6 +826,28 @@
>   }
> </pre>
>
>+    <h2><a id="conditions">Conditional expressions</a></h2>
>+      <p>For readability reasons new code should avoid shortening comparisons
>+        to 0 for numeric types. Boolean and pointer comparisions may be
>+        shortened. All long forms are okay:
>+      </p>
>+<pre>
>+   virFooPtr foos = NULL;
>+   size nfoos = 0;
>+   bool hasFoos = false;
>+
>+GOOD:
>+    if (!foos)
>+    if (!hasFoos)
>+    if (nfoos == 0)
>+    if (foos == NULL)
>+    if (hasFoos == true)
>+
>+BAD:
>+    if (!nfoos)
>+    if (foos)

why is this bad when it is a pointer?  Typo?

>+</pre>
>+
>     <h2><a id="preprocessor">Preprocessor</a></h2>
>
>     <p>Macros defined with an ALL_CAPS name should generally be
>-- 
>2.21.0
>
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