tor-browser

commit 69f55982c0aa8f82864fd0a7435204232b802fc8
parent ff8afcd8c4b4fea7f1affb9ebbe38cab23caf8cb
Author: Steve Fink <sfink@mozilla.com>
Date:   Wed, 10 Dec 2025 22:26:32 +0000

Bug 2005302 - Add mozLog("...") to dynamically set $MOZ_LOG logging levels for JS shell r=mgaudet

Differential Revision: https://phabricator.services.mozilla.com/D275852

Diffstat:
M
js/src/shell/js.cpp
 | 
62
++++++++++++++++++++++++++++++++++++++++++++++++++------------

1 file changed, 50 insertions(+), 12 deletions(-)
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
@@ -405,25 +405,22 @@ static void ToLower(const char* src, char* dest, size_t len) {
   }
 }
 
-// Run this after initialiation!
-void ParseLoggerOptions() {
-  char* mixedCaseOpts = getenv("MOZ_LOG");
-  if (!mixedCaseOpts) {
-    return;
-  }
-
+// This should be run once after initialization, and may be rerun (via the
+// mozLog() command) again later.
+static void ParseLoggerOptions(mozilla::Range<const char> mixedCaseOpts) {
   // Copy into a new buffer and lower case to do case insensitive matching.
   //
   // Done this way rather than just using strcasestr because Windows doesn't
   // have strcasestr as part of its base C library.
-  size_t len = strlen(mixedCaseOpts);
+  size_t len = mixedCaseOpts.length();
   mozilla::UniqueFreePtr<char[]> logOpts(
       static_cast<char*>(calloc(len + 1, 1)));
   if (!logOpts) {
     return;
   }
 
-  ToLower(mixedCaseOpts, logOpts.get(), len);
+  ToLower(mixedCaseOpts.begin().get(), logOpts.get(), len);
+  logOpts.get()[len] = '\0';
 
   // This is a really permissive parser, but will suffice!
   for (auto& logger : logModules) {
@@ -433,11 +430,13 @@ void ParseLoggerOptions() {
       mozilla::UniqueFreePtr<char[]> lowerName(
           static_cast<char*>(calloc(len + 1, 1)));
       ToLower(logger->name, lowerName.get(), len);
+      lowerName.get()[len] = '\0';
 
+      int logLevel = 0;
       if (char* needle = strstr(logOpts.get(), lowerName.get())) {
         // If the string to enable a logger is present, but no level is provided
         // then default to Debug level.
-        int logLevel = static_cast<int>(mozilla::LogLevel::Debug);
+        logLevel = static_cast<int>(mozilla::LogLevel::Debug);
 
         if (char* colon = strchr(needle, ':')) {
           // Parse character after colon as log level.
@@ -448,12 +447,41 @@ void ParseLoggerOptions() {
 
         fprintf(stderr, "[JS_LOG] Enabling Logger %s at level %d\n",
                 logger->name, logLevel);
-        logger->level = mozilla::ToLogLevel(logLevel);
+      } else {
+        if (logger->level != mozilla::ToLogLevel(logLevel)) {
+          fprintf(stderr, "[JS_LOG] Resetting Logger %s to level %d\n",
+                  logger->name, logLevel);
+        }
       }
+
+      logger->level = mozilla::ToLogLevel(logLevel);
     }
   }
 }
 
+static bool SetMozLog(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  Rooted<JSString*> spec(cx, ToString(cx, args.get(0)));
+  if (!spec) {
+    return false;
+  }
+
+  if (!spec->hasLatin1Chars()) {
+    JS_ReportErrorASCII(cx, "invalid MOZ_LOG setting");
+    return false;
+  }
+
+  AutoStableStringChars stable(cx);
+  if (!stable.init(cx, spec)) {
+    return false;
+  }
+
+  mozilla::Range<const Latin1Char> r = stable.latin1Range();
+  ParseLoggerOptions({(const char*)r.begin().get(), r.length()});
+  return true;
+}
+
 /*
  * Limit the timeout to 30 minutes to prevent an overflow on platfoms
  * that represent the time internally in microseconds using 32-bit int.
@@ -10878,6 +10906,13 @@ TestAssertRecoveredOnBailout,
 "decompressLZ4(bytes)",
 " Return a decompressed copy of bytes using LZ4."),
 
+    JS_FN_HELP("mozLog", SetMozLog, 0, 0,
+"mozLog(\"logLevels\")",
+"  Modify log levels as if MOZ_LOG had been set to this at startup.\n"
+"      `logLevels` is a comma-separated list of log modules, each\n"
+"      with an optional \":<level>\" (defaults to 5 aka Debug).\n"
+"      example: mozLog('gc,wasm:4')"),
+
     JS_FS_HELP_END
 };
 // clang-format on
@@ -12707,7 +12742,10 @@ int main(int argc, char** argv) {
   if (!JS::SetLoggingInterface(shellLoggingInterface)) {
     return 1;
   }
-  ParseLoggerOptions();
+  char* logopts = getenv("MOZ_LOG");
+  if (logopts) {
+    ParseLoggerOptions(mozilla::Range(logopts, strlen(logopts)));
+  }
 
   // Start the engine.
   if (const char* message = JS_InitWithFailureDiagnostic()) {