Bug 891266 - Allow to enable faulty.lib debug log at runtime. r=nfroyd

mozglue/linker/ElfLoader.cpp

@@ -289,6 +289,9 @@ ElfLoader ElfLoader::Singleton;
 TemporaryRef<LibHandle>
 ElfLoader::Load(const char *path, int flags, LibHandle *parent)
 {
+  /* Ensure logging is initialized or refresh if environment changed. */
+  Logging::Init();
+
   RefPtr<LibHandle> handle;
 
   /* Handle dlopen(NULL) directly. */
@@ -313,9 +316,7 @@ ElfLoader::Load(const char *path, int flags, LibHandle *parent)
   }
 
   char *abs_path = NULL;
-#ifdef MOZ_DEBUG_LINKER
   const char *requested_path = path;
-#endif
 
   /* When the path is not absolute and the library is being loaded for
    * another, first try to load the library from the directory containing
@@ -410,6 +411,9 @@ ElfLoader::Register(LibHandle *handle)
 void
 ElfLoader::Forget(LibHandle *handle)
 {
+  /* Ensure logging is initialized or refresh if environment changed. */
+  Logging::Init();
+
   LibHandleList::iterator it = std::find(handles.begin(), handles.end(), handle);
   if (it != handles.end()) {
     DEBUG_LOG("ElfLoader::Forget(%p [\"%s\"])", reinterpret_cast<void *>(handle),
@@ -981,3 +985,5 @@ SEGVHandler::__wrap_sigaction(int signum, const struct sigaction *act,
     that.action = *act;
   return 0;
 }
+
+Logging Logging::Singleton;

mozglue/linker/Logging.h

@@ -5,6 +5,8 @@
 #ifndef Logging_h
 #define Logging_h
 
+#include "mozilla/Likely.h"
+
 #ifdef ANDROID
 #include <android/log.h>
 #define LOG(...) __android_log_print(ANDROID_LOG_ERROR, "GeckoLinker", __VA_ARGS__)
@@ -36,11 +38,35 @@
 
 #endif
 
-#ifdef MOZ_DEBUG_LINKER
-#define DEBUG_LOG LOG
-#else
-#define DEBUG_LOG(...)
-#endif
+class Logging
+{
+public:
+  static bool isVerbose()
+  {
+    return Singleton.verbose;
+  }
+
+private:
+  bool verbose;
+
+public:
+  static void Init()
+  {
+    const char *env = getenv("MOZ_DEBUG_LINKER");
+    if (env && *env == '1')
+      Singleton.verbose = true;
+  }
+
+private:
+  static Logging Singleton;
+};
+
+#define DEBUG_LOG(...)   \
+  do {                   \
+    if (MOZ_UNLIKELY(Logging::isVerbose())) {  \
+      LOG(__VA_ARGS__);  \
+    }                    \
+  } while(0)
 
 /* HAVE_64BIT_OS is not defined when building host tools, so use
  * __SIZEOF_POINTER__ */

mozglue/linker/szip.cpp

@@ -18,6 +18,8 @@
 #include "Utils.h"
 #include "Logging.h"
 
+Logging Logging::Singleton;
+
 const char *filterName[] = {
   "none",
   "thumb",
@@ -470,6 +472,8 @@ int main(int argc, char* argv[])
   SeekableZStream::FilterId filter = SzipCompress::DEFAULT_FILTER;
   size_t dictSize = (size_t) 0;
 
+  Logging::Init();
+
   for (firstArg = &argv[1]; argc > 2; argc--, firstArg++) {
     if (!firstArg[0] || firstArg[0][0] != '-')
       break;