Copyright	(c) 2026 Tushar Adhatrao
License	MIT
Stability	stable
Safe Haskell	None
Language	GHC2021

WasmEdge.Log

Contents

Log levels
Level control
Custom callback

Description

Configure the WasmEdge logging system. The logging system is a global singleton — configuration affects all WasmEdge operations in the process.

Example:

import WasmEdge.Log

main :: IO ()
main = do
  setLogLevel Error
  -- ... run WasmEdge operations ...
  logOff  -- silence all output

Synopsis

data LogLevel
- = LogTrace
- | LogDebug
- | LogInfo
- | LogWarn
- | LogError
- | LogCritical
setLogLevel :: LogLevel -> IO ()
setLogError :: IO ()
setLogDebug :: IO ()
logOff :: IO ()
data LogMessage = LogMessage {
- logMsgText :: !Text
- logMsgLogger :: !Text
- logMsgLevel :: !LogLevel
}
setLogCallback :: (LogMessage -> IO ()) -> IO ()
clearLogCallback :: IO ()

Log levels

data LogLevel #

The WasmEdge log verbosity level.

Constructors

LogTrace	Trace-level (most verbose)
LogDebug	Debug-level
LogInfo	Informational
LogWarn	Warnings only
LogError	Errors only
LogCritical	Critical errors only

Instances

Instances details

Bounded LogLevel #
Instance details Defined in WasmEdge.Log Methods minBound :: LogLevel # maxBound :: LogLevel #
Enum LogLevel #
Instance details Defined in WasmEdge.Log Methods succ :: LogLevel -> LogLevel # pred :: LogLevel -> LogLevel # toEnum :: Int -> LogLevel # fromEnum :: LogLevel -> Int # enumFrom :: LogLevel -> [LogLevel] # enumFromThen :: LogLevel -> LogLevel -> [LogLevel] # enumFromTo :: LogLevel -> LogLevel -> [LogLevel] # enumFromThenTo :: LogLevel -> LogLevel -> LogLevel -> [LogLevel] #
Show LogLevel #
Instance details Defined in WasmEdge.Log Methods showsPrec :: Int -> LogLevel -> ShowS # show :: LogLevel -> String # showList :: [LogLevel] -> ShowS #
Eq LogLevel #
Instance details Defined in WasmEdge.Log Methods (==) :: LogLevel -> LogLevel -> Bool # (/=) :: LogLevel -> LogLevel -> Bool #
Ord LogLevel #
Instance details Defined in WasmEdge.Log Methods compare :: LogLevel -> LogLevel -> Ordering # (<) :: LogLevel -> LogLevel -> Bool # (<=) :: LogLevel -> LogLevel -> Bool # (>) :: LogLevel -> LogLevel -> Bool # (>=) :: LogLevel -> LogLevel -> Bool # max :: LogLevel -> LogLevel -> LogLevel # min :: LogLevel -> LogLevel -> LogLevel #

Level control

setLogLevel :: LogLevel -> IO () #

Set the global log level.

setLogError :: IO () #

Shortcut: set log level to LogError.

setLogDebug :: IO () #

Shortcut: set log level to LogDebug.

logOff :: IO () #

Disable all logging output.

Custom callback

data LogMessage #

A structured log message delivered to a custom log callback.

Constructors

LogMessage
Fields logMsgText :: !Text The log message text. logMsgLogger :: !Text The name of the logger that produced this message. logMsgLevel :: !LogLevel The severity level.

Instances

Instances details

Show LogMessage #
Instance details Defined in WasmEdge.Log Methods showsPrec :: Int -> LogMessage -> ShowS # show :: LogMessage -> String # showList :: [LogMessage] -> ShowS #
Eq LogMessage #
Instance details Defined in WasmEdge.Log Methods (==) :: LogMessage -> LogMessage -> Bool # (/=) :: LogMessage -> LogMessage -> Bool #

setLogCallback :: (LogMessage -> IO ()) -> IO () #

Set a custom log callback. The callback replaces any previously set one. The old callback's FunPtr is freed automatically.

The raw C struct layout of WasmEdge_LogMessage is:

typedef struct WasmEdge_LogMessage {
  WasmEdge_String Message;    // offset 0
  WasmEdge_String LoggerName; // offset 16
  WasmEdge_LogLevel Level;    // offset 32
  time_t Time;                // offset 36 (platform-dependent)
  uint64_t ThreadId;          // ...
} WasmEdge_LogMessage;

We parse the relevant fields via fixed offsets.

clearLogCallback :: IO () #

Remove the custom log callback and restore default logging.