Libunit: added macros that enhance type safety.

nxt_min()
nxt_max()
    Return the minimum/maximum of two values.

nxt_swap()
    Swap the values of two variables passed by their addresses.

nxt_sizeof_array()
    Return the size (in bytes) of an array.

nxt_nitems()
    Return the number of elements in an array.

nxt_memberof()
    Expand to a member of a structure.  It uses a compound literal for
    the object.

nxt_sizeof_incomplete()
    Calculate the size of an incomplete type, as if sizeof() could be
    applied to it.

nxt_sizeof_fam0()
    Calculate the size of each element of a FAM of a structure.

nxt_sizeof_fam()
    Calculate the size of a FAM of a structure.

nxt_offsetof_fam()
    Calculate the offset of the nth element of the FAM from the start of
    the containing structure.

nxt_sizeof_struct()
    Calculate the total size of a structure containing a FAM.  This
    value is the one that should be used for allocating the structure.

    Suggested-by: Andrew Clayton <a.clayton@nginx.com>

nxt_is_near_end()
    Evaluate to true if the member is near the end of a structure.  This
    is only designed to be used with FAMs, to make sure that the FAM is
    near the end of the structure (a zero-length array near the end of
    the structure would still pass this test, but it's a reasonable
    assertion to do.

    Suggested-by: David Laight <David.Laight@ACULAB.COM>

nxt_is_zero_sizeof()
    Evaluate to true if the size of 'x' is 0.

nxt_is_same_type()
    Evaluate to true if the both arguments are compatible types.

nxt_is_same_typeof()
    Evaluate to true if the types of both arguments are compatible.

nxt_is_array()
    Evaluate to true if the argument is an array.

nxt_must_be()
    It's like static_assert(3), but implemented as an expression.  It's
    necessary for writing the must_be_array() macro.  It's always
    evaluates to (int) 0.

nxt_must_be_array()
    Statically assert that the argument is an array.  It is an
    expression that always evaluates to (int) 0.

nxt_must_be_zero_sizeof()
    Statically assert that the argument has a size of 0.

nxt_must_be_near_end()
    Statically assert that a member of a structure is near the end of
    it.

    Suggested-by: David Laight <David.Laight@ACULAB.COM>

nxt_must_be_fam()
    Statically assert that the argument is a flexible array member
    (FAM).  It's an expression that always evaluates to (int) 0.

Link: <https://gustedt.wordpress.com/2011/03/14/flexible-array-member/>
Link: <https://lore.kernel.org/lkml/202308161913.91369D4A@keescook/T/>
Link: <https://inbox.sourceware.org/gcc/dac8afb7-5026-c702-85d2-c3ad977d9a48@kernel.org/T/>
Link: <https://stackoverflow.com/a/57537491>
Link: <https://github.com/shadow-maint/shadow/pull/762>
Cc: Andrew Clayton <a.clayton@nginx.com>
Cc: Zhidao Hong <z.hong@f5.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

1 files changed, 4 insertions, 13 deletions

diff --git a/src/nxt_clang.h b/src/nxt_clang.h
index 94638346..10ed6687 100644
--- a/src/nxt_clang.h
+++ b/src/nxt_clang.h
@@ -8,6 +8,9 @@
 #define _NXT_CLANG_H_INCLUDED_
 
 
+#include <nxt_unit_cdefs.h>
+
+
 #define nxt_inline     static inline __attribute__((always_inline))
 #define nxt_noinline   __attribute__((noinline))
 #define nxt_cdecl
@@ -210,24 +213,12 @@ nxt_popcount(unsigned int x)
     *(type *) ((u_char *) p + offset)
 
 
-#define nxt_nitems(x)                                                         \
-    (sizeof(x) / sizeof((x)[0]))
-
-
 /* GCC and Clang use __builtin_abs() instead of libc abs(). */
 
 #define nxt_abs(val)                                                          \
     abs(val)
 
 
-#define nxt_max(val1, val2)                                                   \
-    ((val1 < val2) ? (val2) : (val1))
-
-
-#define nxt_min(val1, val2)                                                   \
-    ((val1 > val2) ? (val2) : (val1))
-
-
 #define nxt_bswap32(val)                                                      \
     (   ((val)               >> 24)                                           \
      | (((val) & 0x00FF0000) >>  8)                                           \
@@ -252,7 +243,7 @@ nxt_popcount(unsigned int x)
 
 
 #define nxt_length(s)                                                         \
-    (sizeof(s) - 1)
+    (sizeof(s) - 1 + nxt_must_be_array(s))
 
 
 #endif /* _NXT_CLANG_H_INCLUDED_ */