What is the typdef size_t actual code definition

Asked Nov 07 '18 at 14:54

Active Nov 07 '18 at 14:57

Viewed 129 times

I am starting to learn c now ,after looking all over I cannot find the actual code definition for size_t in the header files.

I am trying to understand how this is defined because I believe it is system dependent.

Can someone direct/show the actual definition code.

asked Nov 07 '18 at 14:54

Yinon Dotan

`sizeof` is an operator, not a function. – Fiddling Bits Nov 07 '18 at 14:55
Where did you look? The first header to check is `stddef.h` – StoryTeller - Unslander Monica Nov 07 '18 at 14:56
checked it cannot see can you copy – Yinon Dotan Nov 07 '18 at 14:56
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"I am trying to understand how this is defined because I believe it is system dependent." Indeed. "Can someone direct/show the actual definition code." No, because it is system dependent... – Lundin Nov 07 '18 at 14:57
But it is defined somewhere in the header or am I wrong? – Yinon Dotan Nov 07 '18 at 14:58
@YinonDotan You need to be able to find the stddef.h file and look inside it. If you can not find the file or the definition of size_T, your compiler installation is broken. – Terry Carmen Nov 07 '18 at 14:58
If you really took a peek inside the header, you probably noticed it includes other system specific headers. So your search continues... – StoryTeller - Unslander Monica Nov 07 '18 at 14:58
size_t is a type definition of unsigned. – SPlatten Nov 07 '18 at 14:59
But nowhere in the header I see a line starting with typedef size_t . – Yinon Dotan Nov 07 '18 at 15:00
What compiler are you using? – SPlatten Nov 07 '18 at 15:00
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It doesn't have to be *directly* in that header. It could be added by a system specific header `stddef.h` includes itself. – StoryTeller - Unslander Monica Nov 07 '18 at 15:01
@YinonDotan You shouldn't expect `typedef size_t whatever`, but `typedef whatever size_t`. – Milack27 Nov 07 '18 at 15:01
@StoryTeller, that's not correct, the header my be included by another header but if not defined then a compiler error will result. – SPlatten Nov 07 '18 at 15:01
I looked at the code in github – Yinon Dotan Nov 07 '18 at 15:02
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@SPlatten - I suspect you misunderstood my comment. – StoryTeller - Unslander Monica Nov 07 '18 at 15:03
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https://github.com/gcc-mirror/gcc/blob/master/gcc/ginclude/stddef.h. These aren't exactly user-friendly reading, as they are portable to all manner of systems. It says `typedef __SIZE_TYPE__ size_t;` and then in turn you have `#define __SIZE_TYPE__ long unsigned int` before that. For whatever system this was intended. – Lundin Nov 07 '18 at 15:03
@StoryTeller, fair enough. – SPlatten Nov 07 '18 at 15:03
I there a code or no that is the question. – Yinon Dotan Nov 07 '18 at 15:04
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@YinonDotan, its compiler and language dependant, c or c++ and compiler would be helpful. – SPlatten Nov 07 '18 at 15:04
Lundin THank you . – Yinon Dotan Nov 07 '18 at 15:05
@StoryTeller: it doesn't have to be physically present in any header file. It could be added automatically by the compiler when it notices the inclusion of a system header. – rici Nov 07 '18 at 15:10
@rici - It could. Are you familiar with an implementation that does it like that? Would be an interesting case study – StoryTeller - Unslander Monica Nov 07 '18 at 15:11
@StoryTeller: not an extent example, but there are (or were) embedded compilers in which all systems headers are virtual to avoid filesystem dependency. But more common is for the compiler to have a builtin `__size_t` or some such and for `stddef.h` to have `typedef __size_t size_t` which provides no useful information for OP. – rici Nov 07 '18 at 15:35

What is the typdef size_t actual code definition

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