Re: "undefined behavior"?

On 13/06/2024 00:34, DFS wrote:

On 6/12/2024 6:22 PM, Keith Thompson wrote:

Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:

On 12.06.2024 22:47, DFS wrote:

[...]

before: char outliers[100];
after : char outliers[100] = "";

[...]

Seriously; why do you expect [in C] a declaration to initialize that
stack object? (There are other languages that do initializations as
the language defines it, but C doesn't; it may help to learn before
programming in any language?) And why do you think that "" would be
an appropriate initialization (i.e. a single '\0' character) and not
all 100 elements set to '\0'? (Someone else might want to access the
element 'answer[99]'.) And should we pay for initializing 1000000000
characters in case one declares an appropriate huge array?

>
This:
     char outliers[100] = "";
initializes all 100 elements to zero.  So does this:
     char outliers[100] = { '\0' };
Any elements or members not specified in an initializer are set to zero.

Yes.  It's good to point that out, since people might assume that using a string literal here only initialises the bit covered by that string literal.
(In C23 you can also write "char outliers[100] = {};" to get all zeros.)

>
If you want to set an array's 0th element to 0 and not waste time
initializing the rest, you can assign it separately:
     char outliers[100];
     outliers[0] = '\0';
or
     char outliers[100];
     strcpy(outliers, "");
though the overhead of the function call is likely to outweigh the
cost of initializing the array.

A good compiler will generate the same code for both cases - strcpy() is often inlined for such uses.

 Thanks.  I'll have to remember these things.  I like to use char arrays.
 The problem is I don't use C very often, so I don't develop muscle memory.
 

What programming language do you usually use?  And why are you writing in C instead?  (Or do you simply not do much programming?)