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56 lines
2.0 KiB
C++
56 lines
2.0 KiB
C++
/* Compile-time assert-like macros.
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Copyright (C) 2005 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 2, 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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/* Written by Paul Eggert and Jim Meyering. */
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#ifndef VERIFY_H
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# define VERIFY_H 1
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/* Each of these macros verifies that its argument R is a nonzero
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constant expression. To be portable, R's type must be integer (or
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boolean). Unlike assert, 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, where it
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may be cast to void if need be. verify (R) is for declaration
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contexts, e.g., the top level.
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The symbols verify_error_if_negative_size__ and verify_function__
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are private to this header. */
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/* Verify requirement R at compile-time, as an integer constant expression.
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Return true. */
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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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# 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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# endif
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/* Verify requirement R at compile-time, as a declaration without a
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trailing ';'. */
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# define verify(R) extern int (* verify_function__ (void)) [verify_true (R)]
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#endif
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