The tls_model attribute
The tls_model attribute allows source-level control for the thread-local storage
model used for a given variable. The tls_model attribute
must specify one of local-exec, initial-exec, local-dynamic, or global-dynamic access method, which overrides the -ftls-model (-qtls) option for that variable. For example:
__thread int i __attribute__((tls_model("local-exec")));
The tls_model attribute allows the linker to check that the correct thread model has been used to build the application or shared library. The linker/loader behavior is as follows:
Access method | Link-time diagnostic | Runtime diagnostic |
---|---|---|
local-exec | Fails if referenced symbol is imported. | Fails if module is not the main program. Fails if referenced symbol is imported (but the linker should have detected the error already). |
initial-exec | None. | dlopen() fails if referenced symbol is not in the module loaded at execution time. |
local-dynamic | Fails if referenced symbol is imported. | Fails if referenced symbol is imported (but the linker should have detected the error already). |
global-dynamic | None. | None. |