refactor zen command return value handling (#487)

- Improvement: Use consistent language for command line argument parsing errors
- Improvement: Changed zen command parsing errors to output help first and error last to make it easier to spot the error
- Improvement: Refactor zen command return codes to conform to valid Linux range (0-255)

        kSuccess     = 0,
        kOtherError  = 1,
        kBadInput    = 2,

        kOutOfMemory = 16,
        kOutOfDisk   = 17,

        kAssertError = 70,
        
        kHttpOtherClientError = 80,
        kHttpCantConnectError = 81,
        kHttpNotFound         = 66,  // NotFound(404)
        kHttpUnauthorized     = 77,  // Unauthorized(401),
        kHttpSLLError         = 82,
        kHttpForbidden        = 83,  // Forbidden(403)
        kHttpTimeout          = 84,  // RequestTimeout(408)
        kHttpConflict         = 85,  // Conflict(409)
        kHttpNoHost           = 86,
        
        kHttpOtherServerError	   = 90,
        kHttpInternalServerError = 91,  // InternalServerError(500)
        kHttpServiceUnavailable  = 69,  // ServiceUnavailable(503)
        kHttpBadGateway          = 92,  // BadGateway(502)
        kHttpGatewayTimeout      = 93,  // GatewayTimeout(504)

1 files changed, 3 insertions, 3 deletions

diff --git a/src/zen/cmds/bench_cmd.cpp b/src/zen/cmds/bench_cmd.cpp
index d904a51f6..b9c45a328 100644
--- a/src/zen/cmds/bench_cmd.cpp
+++ b/src/zen/cmds/bench_cmd.cpp
@@ -25,14 +25,14 @@ BenchCommand::BenchCommand()
 
 BenchCommand::~BenchCommand() = default;
 
-int
+void
 BenchCommand::Run(const ZenCliOptions& GlobalOptions, int argc, char** argv)
 {
 	ZEN_UNUSED(GlobalOptions);
 
 	if (!ParseOptions(argc, argv))
 	{
-		return 0;
+		return;
 	}
 
 #if ZEN_PLATFORM_WINDOWS
@@ -97,7 +97,7 @@ BenchCommand::Run(const ZenCliOptions& GlobalOptions, int argc, char** argv)
 	}
 #endif
 
-	return 0;
+	return;
 }
 
 }  // namespace zen