mirror of
https://git.savannah.gnu.org/git/gnulib.git
synced 2025-08-08 17:22:05 +03:00
assert-h: new module, which supports C1X-style static_assert
* lib/assert.in.h, m4/assert_h.m4, modules/assert-h: New files. * lib/verify.h: Revamp so that this can be copied into assert.h, while retaining the ability to use it standalone as before. Rename private identifiers so as not to encroach on the standard C namespace, since this is now used by assert.h. (_GL_VERIFY_TYPE): New macro, factoring out differing parts of the old verify_true. (_GL_VERIFY_TRUE): New macro, with much of the contents of the old verify_true. Use _GL_VERIFY_TYPE. (_GL_VERIFY): New macro, with much of the contents of the old verify. (static_assert): New macro, if _GL_STATIC_ASSERT_H is defined and static_assert is not; _GL_STATIC_ASSERT_H is defined when this file is copied into the replacement assert.h. (_Static_assert): New macro, if _GL_STATIC_ASSERT_H is defined and _Static_assert is not built in. (verify_true, verify): Define only if _GL_STATIC_ASSERT_H is not defined, and use the new macros mentioned above. * doc/posix-headers/assert.texi: Document this.
This commit is contained in:
Paul Eggert
22
ChangeLog
22
ChangeLog
@@ -1,3 +1,25 @@
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2011-05-05 Paul Eggert <eggert@cs.ucla.edu>
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assert-h: new module, which supports C1X-style static_assert
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* lib/assert.in.h, m4/assert_h.m4, modules/assert-h: New files.
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* lib/verify.h: Revamp so that this can be copied into assert.h,
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while retaining the ability to use it standalone as before.
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Rename private identifiers so as not to encroach on the
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standard C namespace, since this is now used by assert.h.
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(_GL_VERIFY_TYPE): New macro, factoring out differing parts of
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the old verify_true.
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(_GL_VERIFY_TRUE): New macro, with much of the contents of
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the old verify_true. Use _GL_VERIFY_TYPE.
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(_GL_VERIFY): New macro, with much of the contents of the old verify.
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(static_assert): New macro, if _GL_STATIC_ASSERT_H
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is defined and static_assert is not; _GL_STATIC_ASSERT_H is
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defined when this file is copied into the replacement assert.h.
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(_Static_assert): New macro, if _GL_STATIC_ASSERT_H is defined
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and _Static_assert is not built in.
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(verify_true, verify): Define only if _GL_STATIC_ASSERT_H is not
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defined, and use the new macros mentioned above.
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* doc/posix-headers/assert.texi: Document this.
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2011-05-05 Bruno Haible <bruno@clisp.org>
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fclose, fflush: Respect rules for use of AC_LIBOBJ.
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@@ -3,12 +3,31 @@
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POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/basedefs/assert.h.html}
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Gnulib module: ---
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Gnulib module: assert-h
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See also the Gnulib module @code{assert}.
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Portability problems fixed by Gnulib:
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@itemize
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@item
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The draft C1X and C++0X @code{static_assert}, and the draft C1X
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@code{_Static_assert}, are not supported by many platforms.
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For example, GCC versions before 4.6.0 do not support @code{_Static_assert},
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and G++ versions through at least 4.6.0 do not support @code{static_assert}.
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@end itemize
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Portability problems not fixed by Gnulib:
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@itemize
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@item
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Draft C1X @code{_Static_assert} and draft C++0X @code{static_assert}
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are keywords that can be used without including @code{<assert.h>}.
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The Gnulib substitutes are macros that require including @code{<assert.h>}.
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@item
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The draft C1X @code{static_assert} and @code{_Static_assert} can also
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be used within a @code{struct} or @code{union} specifier, in place of
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an ordinary declaration of a member of the struct or union. The
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Gnulib substitute can be used only as an ordinary declaration.
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@item
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In C99, @code{assert} can be applied to any scalar expression.
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In C89, the argument to @code{assert} is of type @code{int}.
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@end itemize
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28
lib/assert.in.h
Normal file
28
lib/assert.in.h
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@@ -0,0 +1,28 @@
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/* Substitute for and wrapper around <assert.h>
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Copyright (C) 2011 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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/* Do not guard the include, since <assert.h> is supposed to define
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the assert macro each time it is included. */
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#if __GNUC__ >= 3
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@PRAGMA_SYSTEM_HEADER@
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#endif
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@PRAGMA_COLUMNS@
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#@INCLUDE_NEXT@ @NEXT_ASSERT_H@
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/* The definition of static_assert is copied here. */
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130
lib/verify.h
130
lib/verify.h
@@ -17,42 +17,37 @@
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/* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */
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#ifndef VERIFY_H
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# define VERIFY_H 1
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#ifndef _GL_VERIFY_H
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# define _GL_VERIFY_H
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/* Define HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the
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/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per the
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C1X draft N1548 section 6.7.10. This is supported by GCC 4.6.0 and
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later, in C mode, and its use here generates easier-to-read diagnostics
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when verify (R) fails.
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Define HAVE_STATIC_ASSERT to 1 if static_assert works as per the
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C1X draft N1548 section 7.2 or the C++0X draft N3242 section 7.(4).
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Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per the
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C++0X draft N3242 section 7.(4).
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This will likely be supported by future GCC versions, in C++ mode.
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For now, use this only with GCC. Eventually whether _Static_assert
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and static_assert works should be determined by 'configure'. */
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Use this only with GCC. If we were willing to slow 'configure'
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down we could also use it with other compilers, but since this
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affects only the quality of diagnostics, why bother? */
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# if (4 < __GNUC__ || (__GNUC__ == 4 && 6 <= __GNUC_MINOR__)) && !defined __cplusplus
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# define HAVE__STATIC_ASSERT 1
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# define _GL_HAVE__STATIC_ASSERT 1
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# endif
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/* The condition (99 < __GNUC__) is temporary, until we know about the
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first G++ release that supports static_assert. */
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# if (99 < __GNUC__) && defined __cplusplus
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# define HAVE_STATIC_ASSERT 1
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# define _GL_HAVE_STATIC_ASSERT 1
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# endif
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/* Each of these macros verifies that its argument R is nonzero. To
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be portable, R should be an integer constant expression. Unlike
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assert (R), there is no run-time overhead.
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There are two macros, since no single macro can be used in all
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contexts in C. verify_true (R) is for scalar contexts, including
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integer constant expression contexts. verify (R) is for declaration
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contexts, e.g., the top level.
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Symbols ending in "__" are private to this header.
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If _Static_assert works, verify (R) uses it directly. Similarly,
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verify_true (R) works by packaging a _Static_assert inside a struct
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_GL_VERIFY_TRUE works by packaging a _Static_assert inside a struct
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that is an operand of sizeof.
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The code below uses several ideas for C++ compilers, and for C
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@@ -64,7 +59,9 @@
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constant and nonnegative.
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* Next this expression W is wrapped in a type
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struct verify_type__ { unsigned int verify_error_if_negative_size__: W; }.
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struct _gl_verify_type {
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unsigned int _gl_verify_error_if_negative: W;
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}.
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If W is negative, this yields a compile-time error. No compiler can
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deal with a bit-field of negative size.
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@@ -78,7 +75,7 @@
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void function (int n) { verify (n < 0); }
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* For the verify macro, the struct verify_type__ will need to
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* For the verify macro, the struct _gl_verify_type will need to
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somehow be embedded into a declaration. To be portable, this
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declaration must declare an object, a constant, a function, or a
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typedef name. If the declared entity uses the type directly,
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@@ -116,11 +113,11 @@
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Which of the following alternatives can be used?
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extern int dummy [sizeof (struct {...})];
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extern int dummy [sizeof (struct verify_type__ {...})];
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extern int dummy [sizeof (struct _gl_verify_type {...})];
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extern void dummy (int [sizeof (struct {...})]);
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extern void dummy (int [sizeof (struct verify_type__ {...})]);
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extern void dummy (int [sizeof (struct _gl_verify_type {...})]);
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extern int (*dummy (void)) [sizeof (struct {...})];
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extern int (*dummy (void)) [sizeof (struct verify_type__ {...})];
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extern int (*dummy (void)) [sizeof (struct _gl_verify_type {...})];
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In the second and sixth case, the struct type is exported to the
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outer scope; two such declarations therefore collide. GCC warns
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@@ -159,44 +156,75 @@
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possible. */
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# define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)
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/* Verify requirement R at compile-time, as an integer constant expression.
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Return 1. */
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/* Verify requirement R at compile-time, as an integer constant expression
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that returns 1. If R is false, fail at compile-time, preferably
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with a diagnostic that includes the string-literal DIAGNOSTIC. */
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# define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
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(!!sizeof (_GL_VERIFY_TYPE (R, DIAGNOSTIC)))
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# ifdef __cplusplus
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template <int w>
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struct verify_type__ { unsigned int verify_error_if_negative_size__: w; };
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# define verify_true(R) \
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(!!sizeof (verify_type__<(R) ? 1 : -1>))
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# elif HAVE__STATIC_ASSERT
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# define verify_true(R) \
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(!!sizeof \
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(struct { \
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_Static_assert (R, "verify_true (" #R ")"); \
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int verify_dummy__; \
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}))
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# elif HAVE_STATIC_ASSERT
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# define verify_true(R) \
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(!!sizeof \
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(struct { \
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static_assert (R, "verify_true (" #R ")"); \
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int verify_dummy__; \
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}))
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struct _gl_verify_type {
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unsigned int _gl_verify_error_if_negative: w;
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};
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# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
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_gl_verify_type<(R) ? 1 : -1>
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# elif defined _GL_HAVE__STATIC_ASSERT
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# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
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struct { \
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_Static_assert (R, DIAGNOSTIC); \
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int _gl_dummy; \
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}
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# else
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# define verify_true(R) \
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(!!sizeof \
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(struct { unsigned int verify_error_if_negative_size__: (R) ? 1 : -1; }))
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# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
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struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; }
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# endif
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/* Verify requirement R at compile-time, as a declaration without a
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trailing ';'. If R is false, fail at compile-time, preferably
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with a diagnostic that includes the string-literal DIAGNOSTIC.
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Unfortunately, unlike C1X, this implementation must appear as an
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ordinary declaration, and cannot appear inside struct { ... }. */
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# ifdef _GL_HAVE__STATIC_ASSERT
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# define _GL_VERIFY _Static_assert
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# else
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# define _GL_VERIFY(R, DIAGNOSTIC) \
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extern int (*_GL_GENSYM (_gl_verify_function) (void)) \
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[_GL_VERIFY_TRUE (R, DIAGNOSTIC)]
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# endif
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/* _GL_STATIC_ASSERT_H is defined if this code is copied into assert.h. */
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# ifdef _GL_STATIC_ASSERT_H
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# if !defined _GL_HAVE__STATIC_ASSERT && !defined _Static_assert
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# define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC)
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# endif
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# if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert
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# define static_assert _Static_assert /* Draft C1X requires this #define. */
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# endif
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# else
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/* Each of these macros verifies that its argument R is nonzero. To
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be portable, R should be an integer constant expression. Unlike
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assert (R), there is no run-time overhead.
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There are two macros, since no single macro can be used in all
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contexts in C. verify_true (R) is for scalar contexts, including
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integer constant expression contexts. verify (R) is for declaration
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contexts, e.g., the top level. */
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/* Verify requirement R at compile-time, as an integer constant expression.
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Return 1. */
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# define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")")
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/* Verify requirement R at compile-time, as a declaration without a
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trailing ';'. */
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# if HAVE__STATIC_ASSERT
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# define verify(R) _Static_assert (R, "verify (" #R ")")
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# elif HAVE_STATIC_ASSERT
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# define verify(R) static_assert (R, "verify (" #R ")")
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# else
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# define verify(R) \
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extern int (* _GL_GENSYM (verify_function) (void)) [verify_true (R)]
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# define verify(R) _GL_VERIFY (R, "verify (" #R ")")
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# endif
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#endif
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29
m4/assert_h.m4
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29
m4/assert_h.m4
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@@ -0,0 +1,29 @@
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# assert-h.m4
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dnl Copyright (C) 2011 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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dnl From Paul Eggert.
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AC_DEFUN([gl_ASSERT_H],
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[
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ASSERT_H=
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AC_CACHE_CHECK([for static_assert], [gl_cv_static_assert],
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[AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[#include <assert.h>
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static_assert (2 + 2 == 4, "arithmetic doesn't work");
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]],
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[[
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static_assert (sizeof (char) == 1, "sizeof doesn't work");
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]])],
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[gl_cv_static_assert=yes],
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[gl_cv_static_assert=no])])
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if test $gl_cv_static_assert = no; then
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ASSERT_H=assert.h
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gl_NEXT_HEADERS([assert.h])
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fi
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AC_SUBST([ASSERT_H])
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AM_CONDITIONAL([GL_GENERATE_ASSERT_H], [test -n "$ASSERT_H"])
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])
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47
modules/assert-h
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47
modules/assert-h
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@@ -0,0 +1,47 @@
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Description:
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An <assert.h> that conforms to C1X.
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Files:
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lib/assert.in.h
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lib/verify.h
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m4/assert_h.m4
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Depends-on:
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include_next
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configure.ac:
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gl_ASSERT_H
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Makefile.am:
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BUILT_SOURCES += $(ASSERT_H)
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# We need the following in order to create <assert.h> when the system
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# doesn't have one that works with the given compiler.
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if GL_GENERATE_ASSERT_H
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assert.h: assert.in.h verify.h $(top_builddir)/config.status
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$(AM_V_GEN)rm -f $@-t $@ && \
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{ echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */' && \
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sed -e 's|@''INCLUDE_NEXT''@|$(INCLUDE_NEXT)|g' \
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-e 's|@''PRAGMA_SYSTEM_HEADER''@|@PRAGMA_SYSTEM_HEADER@|g' \
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-e 's|@''PRAGMA_COLUMNS''@|@PRAGMA_COLUMNS@|g' \
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-e 's|@''NEXT_ASSERT_H''@|$(NEXT_ASSERT_H)|g' \
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< $(srcdir)/assert.in.h && \
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sed -e 's|_gl_verify|_gl_static_assert|g' \
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-e 's|_GL_VERIFY|_GL_STATIC_ASSERT|g' \
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< $(srcdir)/verify.h; \
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} > $@-t && \
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mv $@-t $@
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else
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assert.h: $(top_builddir)/config.status
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rm -f $@
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endif
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MOSTLYCLEANFILES += assert.h assert.h-t
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Include:
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<assert.h>
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License:
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LGPLv2+
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Maintainer:
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Paul Eggert
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