-qtls

Pragma equivalent

None.

Purpose

Enables recognition of the __thread storage class specifier, which designates variables that are to be allocated thread-local storage; and specifies the threadlocal storage model to be used.

When this option is in effect, any variables marked with the __thread storage class specifier are treated as local to each thread in a multithreaded application. At run time, a copy of the variable is created for each thread that accesses it, and destroyed when the thread terminates. Like other high-level constructs that you can use to parallelize your applications, thread-local storage prevents race conditions to global data, without the need for low-level synchronization of threads.

Suboptions allow you to specify thread-local storage models, which provide better performance but are more restrictive in their applicability.

Syntax


>>- -q--+-tls--+-----------------------+-+---------------------><
        |      |    .-unsupported----. | |   
        |      '-=--+-default--------+-' |   
        |           +-global-dynamic-+   |   
        |           +-initial-exec---+   |   
        |           +-local-exec-----+   |   
        |           '-local-dynamic--'   |   
        '-notls--------------------------'

Defaults

-qtls=unsupported

Parameters

unsupported: The __thread keyword is not recognized and thread-local storage is not enabled. This suboption is equivalent to -qnotls.
global-dynamic: This model is the most general, and can be used for all thread-local variables.
initial-exec: This model provides better performance than the global-dynamic or local-dynamic models, and can be used for thread-local variables defined in dynamically-loaded modules, provided that those modules are loaded at the same time as the executable. That is, it can only be used when all thread-local variables are defined in modules that are not loaded through dlopen.
local-dynamic: This model provides better performance than the global-dynamic model, and can be used for thread-local variables defined in dynamically-loaded modules. However, it can only be used when all references to thread-local variables are contained in the same module in which the variables are defined.
local-exec: This model provides the best performance of all of the models, but can only be used when all thread-local variables are defined and referenced by the main executable.
default: Uses the appropriate model depending on the setting of the -qpic option, which determines whether position-independent code is generated or not. When -qpic is in effect, this suboption results in -qtls=global-dynamic. When -qnopic is in effect, this suboption results in -qtls=initial-exec (-qpic is in effect by default).

Specifying -qtls with no suboption is equivalent to -qtls=default.

Predefined macros