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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Suggested method for returning a string from a C program?
Date: Wed, 19 Mar 2025 11:56:00 -0700
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James Kuyper <jameskuyper@alumni.caltech.edu> writes:
> On 3/19/25 13:23, DFS wrote:
> ...
>>     int64_t n = 0, max = 0, thismax = 0;
> ...
>>     printf("\nmax n = %lld reached at input = %d\n", max, input);
> ...
>> You'll get compilation warnings about the printf specifier used with
>> int64_t.
>
> Not if you use the correct specifier:
> #include <inttypes.h>
> printf("\nmax n = %" PRId64 " reached at input = %d\n", max, input);

Or you can use long long and "%lld" (that's what I did).

long long is at least 64 bits and is guaranteed to exist (in C99
and later, and the autotester uses "gcc -std=c99").  int64_t is
exactly 64 bits and is not guaranteed to exist.  (In every C99 or
later implementation I'm aware of, long long and int64_t are both
exactly 64 bits.)

Another alternative for output is to cast to intmax_t and use "%jd".
(Why "j"?  It was available.)  Input with *scanf() is slightly
trickier; you can't just cast the pointer argument.  (And the
*scanf() functions have undefined behavior on numeric input if the
input is out of range.  fgets() with strto*() is a safer alternative
if you can't be sure what the input is going to look like.)

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */