Shift right on signed integers as arithmetic shift (-logical-signed-right-shift)

Specify that your compiler implements right shifts on signed integers as arithmetic shifts

Since R2023b

Description

The option with this name is available only in the Polyspace Platform (Polyspace Test) user interface. For the equivalent option in the standard Polyspace^® user interface, see Signed right shift (-logical-signed-right-shift).

Specify that your compiler implements right shifts on signed integers as arithmetic shifts (sign bit preserved). Compilers typically implements right shift on signed integers as arithmetic shift instead of logical shift.

If you clear this check box, Polyspace assumes that your compiler performs logical right shifts on signed integers. This option is equivalent to the option Signed right shift (-logical-signed-right-shift).

Set Option

User interface (Polyspace Platform, desktop products only): In your project configuration, the option is on the Build tab on the Target & Compiler node.

Command line: Use the option -logical-signed-right-shift. See Command-Line Information.

Why Use This Option

The C99 Standard (sec 6.5.7) states that for a right-shift operation x1>>x2, if x1 is signed and has negative values, the behavior is implementation-defined. Different compilers choose between arithmetic and logical shift. Use this option to emulate your compiler.

Settings

On (default)

This option indicates that the right shift is arithmetic. That is, during the shift, the sign bit remains:

(-4) >> 1 = -2
(-7) >> 1 = -4
  7  >> 1 = 3

Off

This option indicates that the right shift is logical. That is, 0 replaces the sign bit:

(-4) >> 1 = (-4U) >> 1 = 2147483646
(-7) >> 1 = (-7U) >> 1 = 2147483644
  7  >> 1 = 3

Command-Line Information

When using the command line, arithmetic is the default computation mode. When this option is set, logical computation is performed.

Parameter: -logical-signed-right-shift

Default: Arithmetic signed right shifts

Example (Bug Finder): polyspace-bug-finder -logical-signed-right-shift

Example (Code Prover): polyspace-code-prover -logical-signed-right-shift

Example (Bug Finder Server): polyspace-bug-finder-server -logical-signed-right-shift

Example (Code Prover Server): polyspace-code-prover-server -logical-signed-right-shift

Version History

Introduced in R2023b