Developer Guide and Reference

Contents

Qlong-double

Changes the default size of the long double data type.

Syntax

Linux:
None
macOS:
None
Windows:
/Qlong-double
Arguments
None
Default
OFF
The default size of the long double data type is 64 bits.
Description
This option changes the default size of the long double data type to 80 bits.
However, the alignment requirement of the data type is 16 bytes, and its size must be a multiple of its alignment, so the size of a long double on Windows is also 16 bytes. Only the lower 10 bytes (80 bits) of the 16 byte space will have valid data stored in it.
Note that the Microsoft compiler and Microsoft-provided library routines (such as
printf
or
long double
math functions) do not provide support for 80-bit floating-point values. As a result, this option should only be used when referencing symbols within parts of your application built with this option or symbols in libraries that were built with this option.
Alternate Options
None

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804