问题
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.
回答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.
回答2:
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.
回答3:
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.
回答4:
To address your warning (which is actually an error - you've invoked undefined behavior by passing the wrong type to printf) you should use %zu rather than %d for printing size_t values.
回答5:
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.
回答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.
来源：https://stackoverflow.com/questions/5716774/strlen-to-return-size-t