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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: Which code style do you prefer the most?
Date: Thu, 27 Feb 2025 17:23:41 +0100
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On 27/02/2025 14:05, Ar Rakin wrote:
> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> 
>> On Wed, 26 Feb 2025 13:31:51 -0800, Keith Thompson wrote:
>>
>>> One interesting feature of Perl is that the braces are required.
>>
>> And yet it doesn’t have C-style macros, which to me are the most obvious
>> way one can get into trouble by omitting needed braces.
> 
> What do you mean? Sorry I'm stupid sometimes.

He is thinking of situations like this (ignore the stupidity of the 
example) :

#define message(x) printf("Message: "); printf(x); printf("\n")

void foo(int y) {
	message("Starting foo... ");
	if (y < 0)
		message("Y is negative");
	message("Done foo.")
}

Reading "foo", you'd think that it would print "Message: Y is 
negative\n" if y is negative.  But in fact only the first statement in 
the macro is covered by the conditional, and "Y is negative\n" will 
always be printed.  You can easily imagine how things could get a whole 
lot worse from such mixups.

There are many ways to avoid this, including putting a "do { ... } while 
(0)" wrapper around the statements in the macro, using an inline 
function instead of a macro, writing macro names in all-caps as a 
warning (I strongly dislike that convention), and always using braces 
with conditionals even if they appear to cover just one statement.

I am not sure if there is a basis for judging the "most obvious" problem 
that can occur from omitting braces in conditionals, but this is 
certainly a strong contender for the title.

Another case that occurs is confusion about matching up else's with if's 
in nested conditionals without braces.