Bug 1438866 - Add some utility code to help with debugging. r=emilio

This adds an RAII class and macro that can be quickly added in functions
to log entry/exit from the function. This is useful to debugging.

MozReview-Commit-ID: 4Ud8jLOxI0R

--HG--
extra : rebase_source : 518d30fe44dff67bffb186e23c1eb858c02280af

build/clang-plugin/mozsearch-plugin/MozsearchIndexer.cpp

@@ -69,6 +69,20 @@ static bool isValidIdentifier(std::string Input) {
   return true;
 }
 
+struct RAIITracer {
+  RAIITracer(const char *log) : mLog(log) {
+    printf("<%s>\n", mLog);
+  }
+
+  ~RAIITracer() {
+    printf("</%s>\n", mLog);
+  }
+
+  const char* mLog;
+};
+
+#define TRACEFUNC RAIITracer tracer(__FUNCTION__);
+
 class IndexConsumer;
 
 // For each C++ file seen by the analysis (.cpp or .h), we track a
@@ -444,6 +458,10 @@ public:
       // in different ways are analyzed completely.
       char Buffer[65536];
       FILE *Fp = Lock.openFile("r");
+      if (!Fp) {
+        fprintf(stderr, "Unable to open input file %s\n", Filename.c_str());
+        exit(1);
+      }
       while (fgets(Buffer, sizeof(Buffer), Fp)) {
         Lines.push_back(std::string(Buffer));
       }
@@ -460,6 +478,10 @@ public:
       // Overwrite the output file with the merged data. Since we have the lock,
       // this will happen atomically.
       Fp = Lock.openFile("w");
+      if (!Fp) {
+        fprintf(stderr, "Unable to open output file %s\n", Filename.c_str());
+        exit(1);
+      }
       size_t Length = 0;
       for (std::string &Line : Nodupes) {
         Length += Line.length();