Re: how to make a macro work as a single line if stmt without braces

On 22/09/2024 17:27, Michael S wrote:

On Sun, 22 Sep 2024 16:56:47 +0100
Bart <bc@freeuk.com> wrote:
 

On 22/09/2024 16:11, Kaz Kylheku wrote:

On 2024-09-22, David Brown <david.brown@hesbynett.no> wrote:

I am not suggesting overuse of braces.  I am suggesting /good/ use
of them.
>
<https://www.synopsys.com/blogs/software-security/understanding-apple-goto-fail-vulnerability-2.html>
>
That's perhaps the most famous example of the havoc caused by
omitting useful braces.
>
Consistency and clarity is important.  So is maintainability.
Suppose, for example, you want to add a line "attempts++;"
alongside the "ok++;" line.  When the braces are there, the change
is exactly that - add the new line you want.  Without the original
braces, you are now making changes to the structural syntax of the
code as well when you add in original braces - or you are making a
mistake in the code.

>
My super advanced text editor from the future isn't letting me do
that:
>
    if (failed)
      WARN("failed because...");
    else
      ok++;
    attempts++; // automatic deindent
>
When I add a line after ok++, it deindents it to be at the same
indentation level as the if, before letting me type any content
into it.
>
OK, I lied about the super advanced from the future. It's just Vim.
>
Also GCC has been able to diagnose misleading indentation for some
years now.
>
Between those two, there is nothing to worry about; just
concentrate on whether it looks prettier without the braces or with.
  

>
So, everyone has to write code exactly to the C standard.
>
But when it comes to more practical matters, it's OK to depend on the
arbitrary characteristics and abilities of whichever one of 1001
different text editors we happen to be using.
>
Or we have to use a specific compiler with a specific set of options.
>
  > Also GCC has been able to diagnose misleading indentation for some
  > years now.
>
How many years was that out of the last 52? How exactly do you turn
it on? Since -Wall -Wpedantic -Wextra doesn't report it.
>

 My gcc warns just fine.
 void bar(int);
int foo(int x) {
   if (x)
     bar(x);
     x -= 1;
   return x;
}
 gcc -c -Wall foo.c
 foo.c: In function 'foo':
foo.c:3:3: warning: this 'if' clause does not guard...
[-Wmisleading-indentation] 3 |   if (x)
       |   ^~
foo.c:5:5: note: ...this statement, but the latter is misleadingly
indented as if it were guarded by the 'if'
     5 |     x -= 1;
       |     ^
 

That doesn't pick up a program that in my editor looks like this:
------------------------
int main(void){
total++;
if (failed)
     WARN("failed because...");
else
     ok++;
     failed=0;
}
------------------------
However, the first two indents use four spaces, but the third uses a hard tab that my editor shows as four spaces, but if I print it out to the console, it shows this:
------------------------
int main(void){
total++;
if (failed)
     WARN("failed because...");
else
     ok++;
         failed=0;
}
------------------------
That odd indentation is not picked up either. But it will say something if all indents used spaces or used hard tabs.
If the language has explicit block delimiters (either mandatory braces, or endings like 'end'), then the problem simply wouldn't arise. That 'failed=0' line would either be before the delimiter or after it. The original example would look something like this:
------------------------
if (failed) {
     WARN("failed because...");
} else {
     ok++;
}
     failed=0;
------------------------
That line is still mis-indented, but is now less likely to be taken to be part of that 'else' block.

It is a failure in the design of the language. You can't really
depend on ad hoc features of the tools you use to create and compile
source code.
>
At least guidelines can be used such as always using braces, then
errors can occur less often.
>
(I've been bitten by this endless times when trying to add debugging
statements to existing code. If that code consistently used braces,
then it wouldn't happen.)

 I wonder why I was not bitten by that more than, may be, 5 times in
30+ years. Probably, I am doing something wrong.

How you tried to debug other people's code via adding printf statements at strategic points?