Re: [Help-bash] Why is "volatile" used in bash source code?

[Eric Blake]

On 2/6/19 12:00 PM, Peng Yu wrote:
> Hi,
> 
> I don't understand why "volatile" is used in bash source code. Could
> anybody help me understand why they are used? Thanks.

Which line of code in particular? Ask a vague question, and you'll get a
vague answer, which is:

One of the common uses for volatile is for performing correct
interactions between signal handlers and a main event loop - the
volatile keyword is essential to telling the compiler that a particular
variable might change externally (namely, in the course of a signal
handler that executes between when the variable was set earlier in a
function and then read later in the function), and therefore the
compiler must access memory every time rather than caching the
variable's last value in a register and missing out on the external change.

Now, if you ask about a PARTICULAR file/function/line of code that uses
volatile, I can give you more details why that particular use requires
the keyword.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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