RE: [EXTERNAL]: Re: Why int32_t is long int on 32 Bit Intel?

["panda.trooper" <panda.trooper@protonmail.com>]

Hi Jon,

you are right, in recent GCC/newlib combinations it is GCC who decides by means of setting __INT32_TYPE__, and newlib takes whatever is defined in __INT32_TYPE__. However, in older newlib versions this was not the case. In the good old days the decision was made like this (newlib/libc/include/stdint.h in newlib version 1.18):

/* Check if "long" is 64bit or 32bit wide */
#if __STDINT_EXP(LONG_MAX) > 0x7fffffff
#define __have_long64 1
#elif __STDINT_EXP(LONG_MAX) == 0x7fffffff && !defined(__SPU__)
#define __have_long32 1
#endif
[...]
#if __have_long32
typedef signed long int32_t;
typedef unsigned long uint32_t;
#define __int32_t_defined 1
#elif __STDINT_EXP(INT_MAX) == 0x7fffffffL
typedef signed int int32_t;
typedef unsigned int uint32_t;
#define __int32_t_defined 1
[...]

Please notice "&& !defined(__SPU__)", which is an very interesting exception from the default case. In gcc/config/newlib-stdint.h you find references to this in form of the comment (just from before your excerpt):

/* newlib uses 32-bit long in certain cases for all non-SPU
   targets.  */
#ifndef STDINT_LONG32
#define STDINT_LONG32 (LONG_TYPE_SIZE == 32)
#endif

So the roots of this decision are in the history of newlib. I also assumed that those people who created gcc/config/newlib-stdint.h have quite some stakes in newlib (or the other way around). That's why I asked in this community.

Your explanation with Turbo C is also plausible. Thanks for that interesting insight.

One final question: do you know what "SPU" means in this context and why it is an exceptional case?

Cheers,
Zoltan

------- Original Message -------
On Friday, July 28th, 2023 at 22:23, Jon Beniston <jon@beniston.com> wrote:


> > So again, just out of curiosity: what is the reason using long as int32_t on an architecture where int is suitable, too?
> 
> 
> Long ago, there were 32-bit x86 compilers where int was 16-bit (E.g. Turbo C).
> 
> Also, are you sure it isn't gcc that's determining the type of int32_t rather than Newlib? I've not used i686-elf-gcc, but for some targets newlib defines int32_t based on INT32_TYPE which is defined by gcc:
> 
> In gcc/config/newlib-stdint.h
> 
> #ifndef STDINT_LONG32
> #define STDINT_LONG32 (LONG_TYPE_SIZE == 32)
> #endif
> ...
> #define INT32_TYPE (STDINT_LONG32 ? "long int" : INT_TYPE_SIZE == 32 ? "int" : SHORT_TYPE_SIZE == 32 ? "short int" : CHAR_TYPE_SIZE == 32 ? "signed char" : 0)
> 
> Cheers,
> Jon