Merge patch series "integer limit macro consolidation"

Rasmus Villemoes <ravi@prevas.dk> says:

I was bitten by our limit macros not being usable in #if conditionals
when building a standalone app. It turns out that the work to fix that
had already been started by the inclusion of the mbedtls library, so
it's something that people do hit.

Let's finish the job by providing suitable limit macros for all three families:

- Standard C types, char, short, ...
- Kernel-style fixed-width types s8, u64, ...
- POSIX/C99 fixed-width types int16_t, uint32_t, ...

Please note that a naive approach like spelling out the full decimal
value for the constants doesn't really work, as there is no such thing
as a "negative integer constant". That is, doing

#define LLONG_MIN -9223372036854775808LL

would lead to the compiler complaining

  warning: integer constant is so large that it is unsigned

and the type of that LLONG_MIN would actually be "unsigned long long", so e.g.

#if LLONG_MIN >= 0
#warning "LLONG_MIN is not negative?"
#endif

would fire.

Link: https://lore.kernel.org/r/20250707203655.613340-1-ravi@prevas.dk

3 files changed, 55 insertions, 31 deletions

diff --git a/include/limits.h b/include/limits.h
index 1d0bbf69be7..a032bc5b84d 100644
--- a/include/limits.h
+++ b/include/limits.h
@@ -3,11 +3,61 @@
 #ifndef _LIMITS_H
 #define _LIMITS_H
 
-#define INT_MAX     0x7fffffff
-#define UINT_MAX    0xffffffffU
+#define SCHAR_MAX   __SCHAR_MAX__
+#define SCHAR_MIN   (-SCHAR_MAX - 1)
+#define UCHAR_MAX   (SCHAR_MAX * 2 + 1)
+
+#ifdef __CHAR_UNSIGNED__
+#define CHAR_MAX    UCHAR_MAX
+#define CHAR_MIN    0
+#else
+#define CHAR_MAX    SCHAR_MAX
+#define CHAR_MIN    SCHAR_MIN
+#endif
+
+#define SHRT_MAX    __SHRT_MAX__
+#define SHRT_MIN    (-SHRT_MAX - 1)
+#define USHRT_MAX   (SHRT_MAX * 2 + 1)
+
+#define INT_MAX     __INT_MAX__
+#define INT_MIN     (-INT_MAX - 1)
+#define UINT_MAX    (INT_MAX * 2U + 1U)
+
+#define LONG_MAX    __LONG_MAX__
+#define LONG_MIN    (-LONG_MAX - 1L)
+#define ULONG_MAX   (LONG_MAX * 2UL + 1UL)
+
+#define LLONG_MAX   __LONG_LONG_MAX__
+#define LLONG_MIN   (-LLONG_MAX - 1LL)
+#define ULLONG_MAX  (LLONG_MAX * 2ULL + 1ULL)
+
+#define U8_MAX      UCHAR_MAX
+#define S8_MAX      SCHAR_MAX
+#define S8_MIN      SCHAR_MIN
+#define U16_MAX     USHRT_MAX
+#define S16_MAX     SHRT_MAX
+#define S16_MIN     SHRT_MIN
+#define U32_MAX     UINT_MAX
+#define S32_MAX     INT_MAX
+#define S32_MIN     INT_MIN
+#define U64_MAX     ULLONG_MAX
+#define S64_MAX     LLONG_MAX
+#define S64_MIN     LLONG_MIN
+
+#define UINT8_MAX   U8_MAX
+#define INT8_MAX    S8_MAX
+#define INT8_MIN    S8_MIN
+#define UINT16_MAX  U16_MAX
+#define INT16_MAX   S16_MAX
+#define INT16_MIN   S16_MIN
+#define UINT32_MAX  U32_MAX
+#define INT32_MAX   S32_MAX
+#define INT32_MIN   S32_MIN
+#define UINT64_MAX  U64_MAX
+#define INT64_MAX   S64_MAX
+#define INT64_MIN   S64_MIN
+
 #define CHAR_BIT    8
-#define UINT32_MAX  0xffffffffU
-#define UINT64_MAX  0xffffffffffffffffULL
 
 #if (defined(CONFIG_64BIT) && !defined(CONFIG_SPL_BUILD)) || \
 	(defined(CONFIG_SPL_64BIT) && defined(CONFIG_SPL_BUILD))
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 9467edd65ab..e0443ecac84 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -5,32 +5,6 @@
 #include <linux/printk.h> /* for printf/pr_* utilities */
 #include <limits.h>
 
-#define USHRT_MAX	((u16)(~0U))
-#define SHRT_MAX	((s16)(USHRT_MAX>>1))
-#define SHRT_MIN	((s16)(-SHRT_MAX - 1))
-#define INT_MIN		(-INT_MAX - 1)
-#define LONG_MAX	((long)(~0UL>>1))
-#define LONG_MIN	(-LONG_MAX - 1)
-#define ULONG_MAX	(~0UL)
-#define LLONG_MAX	((long long)(~0ULL>>1))
-#define LLONG_MIN	(-LLONG_MAX - 1)
-#define ULLONG_MAX	(~0ULL)
-
-#define U8_MAX		((u8)~0U)
-#define S8_MAX		((s8)(U8_MAX>>1))
-#define S8_MIN		((s8)(-S8_MAX - 1))
-#define U16_MAX		((u16)~0U)
-#define S16_MAX		((s16)(U16_MAX>>1))
-#define S16_MIN		((s16)(-S16_MAX - 1))
-#define U32_MAX		((u32)~0U)
-#define S32_MAX		((s32)(U32_MAX>>1))
-#define S32_MIN		((s32)(-S32_MAX - 1))
-#define U64_MAX		((u64)~0ULL)
-#define S64_MAX		((s64)(U64_MAX>>1))
-#define S64_MIN		((s64)(-S64_MAX - 1))
-
-#define INT32_MAX	S32_MAX
-
 #define STACK_MAGIC	0xdeadbeef
 
 #define REPEAT_BYTE(x)	((~0ul / 0xff) * (x))
diff --git a/include/stdint.h b/include/stdint.h
index dea83c8226a..90fd2bdee08 100644
--- a/include/stdint.h
+++ b/include/stdint.h
@@ -9,6 +9,6 @@
 #ifndef __UB_STDINT_H
 #define __UB_STDINT_H
 
-#define UINT8_MAX	0xff
+#include <limits.h>
 
 #endif