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Scripting: Reset Lua fake client reply_bytes after command execution.
Lua scripting uses a fake client in order to run commands in the context of a client, accumulate the reply, and convert it into a Lua object to return to the caller. This client is reused again and again, and is referenced by the server.lua_client globally accessible pointer. However after every call to redis.call() or redis.pcall(), that is handled by the luaRedisGenericCommand() function, the reply_bytes field of the client was not set back to zero. This filed is used to estimate the amount of memory currently used in the reply. Because of the lack of reset, script after script executed, this value used to get bigger and bigger, and in the end on 32 bit systems it triggered the following assert: redisAssert(c->reply_bytes < ULONG_MAX-(1024*64)); On 64 bit systems this does not happen because it takes too much time to reach values near to 2^64 for users to see the practical effect of the bug. Now in the cleanup stage of luaRedisGenericCommand() we reset the reply_bytes counter to zero, avoiding the issue. It is not practical to add a test for this bug, but the fix was manually tested using a debugger. This commit fixes issue #656.
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