73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
[assertions.assert]
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# 19 Diagnostics library [[diagnostics]](./#diagnostics)
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## 19.3 Assertions [[assertions]](assertions#assert)
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### 19.3.3 The assert macro [assertions.assert]
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L465)
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If NDEBUG is defined as a macro name
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at the point in the source file where <cassert> is included,
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the assert macro is defined as#define assert(...) ((void)0)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L473)
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Otherwise, the assert macro puts a diagnostic test into programs;
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it expands to an expression of type void which
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has the following effects:
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- [(2.1)](#2.1)
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__VA_ARGS__ is evaluated and contextually converted to bool[.](#2.1.sentence-1)
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- [(2.2)](#2.2)
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If the evaluation yields true there are no further effects[.](#2.2.sentence-1)
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- [(2.3)](#2.3)
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Otherwise, the assert macro's expression
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creates a diagnostic on the standard error stream (ISO/IEC 9899:2024, 7.23.3) in animplementation-defined
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format and calls abort()[.](#2.3.sentence-1)
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The diagnostic contains #__VA_ARGS__ and
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information on
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the name of the source file,
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the source line number, and
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the name of the enclosing function
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(such as provided by source_location::current())[.](#2.3.sentence-2)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L496)
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If __VA_ARGS__ does not expand to
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an [*assignment-expression*](expr.assign#nt:assignment-expression "7.6.19 Assignment and compound assignment operators [expr.assign]"),
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the program is ill-formed[.](#3.sentence-1)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L501)
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The macro assert is redefined according to
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the current state of NDEBUG each time that<cassert> is included[.](#4.sentence-1)
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L506)
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An expression assert(E) is a [constant subexpression](defns.const.subexpr "3.15 constant subexpression [defns.const.subexpr]"), if
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- [(5.1)](#5.1)
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NDEBUG is defined at the point where assert is last defined or redefined, or
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- [(5.2)](#5.2)
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E [contextually converted to bool](conv#def:conversion,contextual_to_bool "7.3 Standard conversions [conv]") is a constant subexpression that evaluates to the value true[.](#5.sentence-1)
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