# Compile time log levels

At compile time the maximum log level can be specified. This allows distros to
disable the overhead code and reduce overall code size.

# Runtime log level

At runtime, the log level is determined by an environment variable. The default
log level is WARNING. The level can be changed by setting the `TSS2_LOG`
environment variable.

Possible levels are: NONE, ERROR, WARNING, INFO, DEBUG, TRACE

The level can be set for all module using the `all` module name or individually
per module. The environment variable is evaluated left to right.

Example: `TSS2_LOG=all+ERROR,marshal+TRACE,tcti+DEBUG`

# Log file

By default, logs are written to standard error (`stderr`). If the environment
variable `TSS2_LOGFILE` is set, the TSS will log to the file at the given path
instead. If the file does not yet exist, it will be created. Otherwise, the TSS
will append to it.

The special value `stderr` will result in default behavior while `stdout` and
`-` will have the TSS write to standard output.

# Implementation

Each source code file specifies its corresponding module before including log.h.
```
#define LOGMODULE tcti
#include "log.h"
```
Optionally, the default log-level for this module can be set:
```
#define LOGMODULE tcti
#define LOGDEFAULT ERROR
#include "log.h"
```