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# Component: errno

#### Macro name

CYGPKG_LIBC_ERRNO

#### Type

Dummy

#### Description

This package controls the behavior of the errno variable (or more strictly, expression) from `errno.h`.

## Option: Per-thread errno

#### Macro name

CYGSEM_LIBC_PER_THREAD_ERRNO

#### Type

Boolean

#### Description

This option controls whether the standard error code reporting variable errno is a per-thread variable, rather than global. Enabling this option will use one slot of kernel per-thread data. You should ensure you have enough slots configured for all your per-thread data.

## Option: Tracing level

#### Macro name

CYGNUM_LIBC_ERRNO_TRACE_LEVEL

#### Type

Count

#### Description

Trace verbosity level for debugging the errno retrieval mechanism in errno.cxx. Increase this value to get additional trace output.

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