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cppdraft/assertions.md

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+[assertions]
+
+# 19 Diagnostics library [[diagnostics]](./#diagnostics)
+
+## 19.3 Assertions [assertions]
+
+### [19.3.1](#general) General [[assertions.general]](assertions.general)
+
+[1](#general-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L452)
+
+The header <cassert> provides a macro for documenting C++ program assertions and a mechanism
+for disabling the assertion checks through defining the macro NDEBUG[.](#general-1.sentence-1)
+
+### [19.3.2](#cassert.syn) Header <cassert> synopsis [[cassert.syn]](cassert.syn)
+
+#define assert(...) *see below*
+
+### [19.3.3](#assert) The assert macro [[assertions.assert]](assertions.assert)
+
+[1](#assert-1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L465)
+
+If NDEBUG is defined as a macro name
+at the point in the source file where <cassert> is included,
+the assert macro is defined as#define assert(...) ((void)0)
+
+[2](#assert-2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L473)
+
+Otherwise, the assert macro puts a diagnostic test into programs;
+it expands to an expression of type void which
+has the following effects:
+
+- [(2.1)](#assert-2.1)
+
+  __VA_ARGS__ is evaluated and contextually converted to bool[.](#assert-2.1.sentence-1)
+
+- [(2.2)](#assert-2.2)
+
+  If the evaluation yields true there are no further effects[.](#assert-2.2.sentence-1)
+
+- [(2.3)](#assert-2.3)
+
+  Otherwise, the assert macro's expression
+creates a diagnostic on the standard error stream (ISO/IEC 9899:2024, 7.23.3) in animplementation-defined
+format and calls abort()[.](#assert-2.3.sentence-1)
+  The diagnostic contains #__VA_ARGS__ and
+information on
+the name of the source file,
+the source line number, and
+the name of the enclosing function
+(such as provided by source_location​::​current())[.](#assert-2.3.sentence-2)
+
+[3](#assert-3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L496)
+
+If __VA_ARGS__ does not expand to
+an [*assignment-expression*](expr.assign#nt:assignment-expression "7.6.19 Assignment and compound assignment operators [expr.assign]"),
+the program is ill-formed[.](#assert-3.sentence-1)
+
+[4](#assert-4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L501)
+
+The macro assert is redefined according to
+the current state of NDEBUG each time that<cassert> is included[.](#assert-4.sentence-1)
+
+[5](#assert-5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L506)
+
+An expression assert(E) is a [constant subexpression](defns.const.subexpr "3.15 constant subexpression [defns.const.subexpr]"), if
+
+- [(5.1)](#assert-5.1)
+
+NDEBUG is defined at the point where assert is last defined or redefined, or
+
+- [(5.2)](#assert-5.2)
+
+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[.](#assert-5.sentence-1)