渴望返回size_t？

Question

In C:
My string length function is returning a size_t value?

Why is it not returning a integer which is conventional? And one more thing I noticed was that when I was trying concatenate this string with another string I received a bus error when I ran the program.

Context: I was kind of playing with gmp library and converting big numbers to strings and I end up with the above situation.

What kind of a string is that? Is my operating system playing a role in this issue? I use a MAC, 64-bit OS.

Edited: The error message I received was:

: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘size_t’

Thanks!

@all: Thanks for the answers but I thought I will put the bus error as another question because it seems to be a different issue.

Answer 1

The problem is int might be not wide enough to store the whole range of possible length values. For example on 64-bit you can have a string longer than 4 gigabytes and if int is 32 bit you can't possibly return length of such a long string via an int variable.

Answer 2

POSIX strlen() does return size_t .

As to what's caused the bus error, it's impossible to say without seeing the code and knowing more details about the exact nature of your changes. One possibility is that you've caused a buffer overrun or did something with a NULL pointer you shouldn't have done.

Answer 3

strlen() always returned size_t ... and the POSIX standard also says that.

I guess the reason is that int has sign and the capacity of even an unsigned int might not be enough for holding size of an element (say if you have a 32bit int on x86-64 with 16GB RAM) ... the example is extreme, but possible.

Answer 4

strlen() returns a size_t since at least ISO C90 -- I just checked in my copy. And this standard should have no technical difference with ANSI C89.

There was a change of convention ( size_t wasn't in K&R C), but it was a long time ago.

Answer 5

要解决您的警告（实际上是一个错误-您通过将错误的类型传递给printf来调用未定义的行为），您应该使用%zu而不是%d来打印size_t值。

Answer 6

There is a very simple and logical reason for all of the functions from the standard library to work with size_t when it comes to lengths of memory blocks - the built-in sizeof operator yields a size_t result as well.

Moreover, size_t is unsigned, of a particular size, tied to the architecture and is semantically different than just a generic int which is meant for storing any number from the count of trees around your office to your SO reputation.