It is possible to devise syntax that can ambiguously be interpreted as either an expression statement or a declaration. Syntax of this sort is called a vexing parse because the compiler must use disambiguation rules to determine the semantic results. The C++ Standard, [stmt.ambig], paragraph 1 [ISO/IEC 14882-2014], states in part:
There is an ambiguity in the grammar involving expression-statements and declarations: An expression-statement with a function-style explicit type conversion as its leftmost subexpression can be indistinguishable from a declaration where the first declarator starts with a
(. In those cases the statement is a declaration. [Note: To disambiguate, the whole statement might have to be examined to determine if it is an expression-statement or a declaration. ...
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Search for other vulnerabilities resulting from the violation of this rule on the CERT website.
Bibliography
| [ISO/IEC 14882-2014] | Subclause 6.8, "Ambiguity Resolution" Subclause 8.2, "Ambiguity Resolution" |
| [Meyers 01] | Item 6, "Be Alert for C++'s Most Vexing Parse" |
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