vm_tools: sommelier: set log-level from cmdline

New style logging uses the syntax `LOG(INFO) << "message";` to indicate
the logging verbosity. That verbosity is tested prior to visible output,
but the selection of which levels will be shown is only controllable at
build-time via '-DLOG_LEVEL=-1'.

There's no practical reason to require such. The test for visibility
_may_ get optimized out by compiler for statically-defined LOG_LEVEL, but
it is a trivial cost not worth optimizing in the general case. Other
tricks can be used to solve that if it becomes an issue.

Now it can be set with --log-level=<int>, with the default set in the
old way with -DLOG_LEVEL=<int>, or defaulting to LOG_LEVEL_INFO (0) when
not defined.

BUG=b:339048928
TEST=sommelier --log-level=-1 ...

Change-Id: I2de93e6c11ccba89022a4aa460c082644328e800
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/5517861
Tested-by: Ryan Neph <[email protected]>
Reviewed-by: Chloe Pelling <[email protected]>
Auto-Submit: Ryan Neph <[email protected]>
Reviewed-by: Arjun Srinivasan <[email protected]>
Commit-Queue: Ryan Neph <[email protected]>

sommelier-logging.cc

@@ -6,6 +6,8 @@
 
 namespace logging {
 
+int64_t min_log_level = LOG_LEVEL;
+
 std::string file_name(std::string file_path) {
   // Extract file name from file path.
   auto found = file_path.find_last_of('/');

sommelier-logging.h

@@ -10,6 +10,7 @@
 #define VM_TOOLS_SOMMELIER_SOMMELIER_LOGGING_H_
 
 #include <cstdarg>
+#include <cstdint>
 #include <cstring>
 #include <iosfwd>
 #include <iostream>
@@ -42,6 +43,12 @@ namespace logging {
 std::string file_name(std::string file_path);
 std::string log_level_to_string(int level);
 
+// not thread-safe
+extern int64_t min_log_level;
+inline void set_min_log_level(int64_t level) {
+  min_log_level = level;
+}
+
 class Log {
  private:
   std::stringstream log_content;
@@ -64,7 +71,7 @@ class Log {
 
   template <typename T>
   Log& operator<<(T const& value) {
-    if (log_level >= LOG_LEVEL) {
+    if (log_level >= min_log_level) {
       this->log_content << value;
     }
     return *this;

sommelier.cc

@@ -3578,6 +3578,8 @@ static void sl_print_usage() {
       "options:\n"
       "  -h, --help\t\t\tPrint this help\n"
       "  -X\t\t\t\tEnable X11 forwarding\n"
+      "  --log-level=LEVEL\t\tSet minimum log level to be processed\n"
+      "\t(allowed range: -1 to 3; lower is more verbose))\n"
       "  --parent\t\t\tRun as parent and spawn child processes\n"
       "  --socket=SOCKET\t\tName of socket to listen on\n"
       "  --display=DISPLAY\t\tWayland display to connect to\n"
@@ -3652,7 +3654,6 @@ static const char* sl_arg_value(const char* arg) {
   return s + 1;
 }
 
-#ifdef QUIRKS_SUPPORT
 // attempts to both split "--argname=argval" and parse "argval" signed integer,
 // or exits the program with a fatal error if detecting any non-integer
 // characters or is out-of-bounds.
@@ -3679,7 +3680,6 @@ static int64_t sl_arg_parse_int_checked(const char* arg) {
   }
   return res;
 }
-#endif  // QUIRKS_SUPPORT
 
 // Parse the list of accelerators that should be reserved by the
 // compositor. Format is "|MODIFIERS|KEYSYM", where MODIFIERS is a
@@ -4084,6 +4084,9 @@ int real_main(int argc, char** argv) {
 
     if (strstr(arg, "--parent") == arg) {
       parent = 1;
+    } else if (strstr(arg, "--log-level") == arg) {
+      const int64_t log_level = sl_arg_parse_int_checked(arg);
+      logging::set_min_log_level(log_level);
     } else if (strstr(arg, "--socket") == arg) {
       socket_name = sl_arg_value(arg);
     } else if (strstr(arg, "--display") == arg) {