Why printf returns int instead of size_t in C

Question

Should the size_t type be returned? Since the size of objects in C is of this type, including the string passed to printf .

Answer 1

Why printf returns int in C?
Shouldn't there be type size_t instead?

It could have been, but of course, an early design decision was to place the return value of the negative EOF to indicate an error.

size_t was a bit late in the early design options. Many functions used by int , where size_t used now on those pre-standard days.

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fprintf() has an environmental limit of "The number of characters that can be obtained with any single conversion must be at least 4095.", so any print that tries to get a long output may encounter this limit before the INT_MAX/SIZE_MAX .

Answer 2

You are pretty much right - in fact printf should return a larger type, since it is theoretically possible to output much more bytes than the size of the largest object that can fit in memory, for example. printf("%s%s", largest_string, largest_string) or even more trivial examples using field width / precision.

The reason is just a historical mistake that we're stuck with. This is especially bad with snprintf , which is artificially constrained by INT_MAX and is forced to return an error if you try to create a longer string with it.

Answer 3

Then the compilers did not require a function declaration to call the function. The return type of a function without declaration or with an undefined return type of int is an implicit rule of int. Some code called printf does not bother pesky #include <stdio.h> .