16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
58 lines
1.8 KiB
Plaintext
58 lines
1.8 KiB
Plaintext
== Why is this an issue?
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When ``++~++`` and ``++<<++`` are applied to small integer types (``++unsigned char++`` or ``++unsigned short++``), the operations are preceded by integral promotion, and the result may contain high-order bits which have not been anticipated.
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=== Noncompliant code example
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[source,cpp]
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----
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unsigned char port = 0x5aU;
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unsigned char result_8;
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unsigned short result_16;
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unsigned short mode;
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result_8 = (~port) >> 4; // Noncompliant; '~port' is 0xFFA5 on a 16-bit machine but 0xFFFFFFA5 on a 32-bit machine. Result is 0xFA for both, but 0x0A may have been expected.
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result_16 = ((port << 4) & mode) >> 6; // Noncompliant; result_16 value depends on the implemented size of an int.
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----
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=== Compliant solution
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[source,cpp]
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----
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result_8 = ((unsigned char)(~port)) >> 4; // Compliant
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result_16 = ((unsigned short)((unsigned short) port << 4) & mode) >> 6; // Compliant
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----
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== Resources
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* MISRA C 2004, 10.5 - If the bitwise operators ~ and << are applied to an operand of _underlying type_ unsigned char or unsigned short, the result shall be immediately cast to the _underlying type_ of the operand.
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* MISRA {cpp} 2008, 5-0-10 - If the bitwise operators ~ and << are applied to an operand with an _underlying type_ of unsigned char or unsigned short, the result shall be immediately cast to the _underlying type_ of the operand.
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Add an explicit cast to the result of the 'x' operator.
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'''
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== Comments And Links
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(visible only on this page)
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=== relates to: S5451
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=== on 21 Oct 2014, 18:34:06 Ann Campbell wrote:
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\[~samuel.mercier] please
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* move the code commentary into the code in the form of comments if needed
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endif::env-github,rspecator-view[]
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