Re: Compile time assert macro
On Fri, 3 May 2013, Stefan Fritsch wrote: I think a CTASSERT macro like in FreeBSD would be nice. It could be used to verify assumptions about type and struct sizes. Ariane suggested making the syntax compatible to the C11 variant. OKs for this version? --- a/sys/lib/libkern/libkern.h +++ b/sys/lib/libkern/libkern.h @@ -138,6 +138,12 @@ abs(int j) #endif #endif +#if __STDC_VERSION__ 201112L +#define_Static_assert(predicate, msg) \ + extern char __static_assert[(predicate) ? 1 : -1 ] \ + __attribute__((__unused__)) +#endif + /* Prototypes for non-quad routines. */ void__assert(const char *, const char *, int, const char *) __attribute__ ((__noreturn__)); --- a/share/man/man9/kern.9 +++ b/share/man/man9/kern.9 @@ -108,6 +108,20 @@ enabled. tests are only included if the kernel has .Dv DEBUG enabled. +.Pp +.nr nS 1 +.Fn _Static_assert CONDITION MESSAGE +.nr nS 0 +.Pp +This is a standard feature in C11 and is implemented as a macro if compiling +with a pre-C11 compiler. +It causes a compile time error if the given condition evaluates to +false. +Its main purpose is to verify assertions about type and struct sizes that +would otherwise make the code fail at run time. +.Fn _Static_assert +can be used in global scope or at the start of blocks, where variable +declarations are allowed. .Sh BYTE STRINGS .nr nS 1 .Ft int
Re: Compile time assert macro
Date: Fri, 17 May 2013 13:24:45 +0200 (CEST) From: Stefan Fritsch s...@sfritsch.de On Fri, 3 May 2013, Stefan Fritsch wrote: I think a CTASSERT macro like in FreeBSD would be nice. It could be used to verify assumptions about type and struct sizes. Ariane suggested making the syntax compatible to the C11 variant. This makes switching between KASSERT and CTASSERT painful. And you have to be creative and add a message string, which then isn't used... NetBSD has CTASSERT as well. I like CTASSERT better. Our kernel is not written in C11. --- a/sys/lib/libkern/libkern.h +++ b/sys/lib/libkern/libkern.h @@ -138,6 +138,12 @@ abs(int j) #endif #endif +#if __STDC_VERSION__ 201112L +#define _Static_assert(predicate, msg) \ + extern char __static_assert[(predicate) ? 1 : -1 ] \ + __attribute__((__unused__)) +#endif + /* Prototypes for non-quad routines. */ void __assert(const char *, const char *, int, const char *) __attribute__ ((__noreturn__)); --- a/share/man/man9/kern.9 +++ b/share/man/man9/kern.9 @@ -108,6 +108,20 @@ enabled. tests are only included if the kernel has .Dv DEBUG enabled. +.Pp +.nr nS 1 +.Fn _Static_assert CONDITION MESSAGE +.nr nS 0 +.Pp +This is a standard feature in C11 and is implemented as a macro if compiling +with a pre-C11 compiler. +It causes a compile time error if the given condition evaluates to +false. +Its main purpose is to verify assertions about type and struct sizes that +would otherwise make the code fail at run time. +.Fn _Static_assert +can be used in global scope or at the start of blocks, where variable +declarations are allowed. .Sh BYTE STRINGS .nr nS 1 .Ft int
Compile time assert macro
Hi, I think a CTASSERT macro like in FreeBSD would be nice. It could be used to verify assumptions about type and struct sizes. This should work on gcc 2.9.5, too, but I haven't tested it. --- sys/lib/libkern/libkern.h +++ sys/lib/libkern/libkern.h @@ -138,6 +138,9 @@ abs(int j) #endif #endif +#defineCTASSERT(x) extern char _ctassert[(x) ? 1 : -1 ] \ + __attribute__((__unused__)) + /* Prototypes for non-quad routines. */ void__assert(const char *, const char *, int, const char *) __attribute__ ((__noreturn__));
