better linux platform impl

command_line.cc

@@ -393,7 +393,8 @@ void IndexMainLoop(IpcClient* client) {
       std::cerr << "Parsing/indexing took " << time.ElapsedMilliseconds() << "ms" << std::endl;
 
       time.Reset();
-      auto response = IpcMessage_IndexTranslationUnitResponse(IndexUpdate(file));
+      IndexUpdate update(file);
+      auto response = IpcMessage_IndexTranslationUnitResponse(update);
       std::cerr << "Creating index update took " << time.ElapsedMilliseconds() << "ms" << std::endl;
 
       time.Reset();

platform_linux.cc

@@ -29,7 +29,7 @@ struct PlatformMutexLinux : public PlatformMutex {
   sem_t* sem_ = nullptr;
 
   PlatformMutexLinux(const std::string& name) {
-    std::cout << "PlatformMutexLinux name=" << name << std::endl;
+    std::cerr << "PlatformMutexLinux name=" << name << std::endl;
     sem_ = sem_open(name.c_str(), O_CREAT, 0666 /*permission*/, 1 /*initial_value*/);
   }
 
@@ -42,7 +42,6 @@ struct PlatformScopedMutexLockLinux : public PlatformScopedMutexLock {
   sem_t* sem_ = nullptr;
 
   PlatformScopedMutexLockLinux(sem_t* sem) : sem_(sem) {
-    std::cout << "PlatformScopedMutexLockLinux" << std::endl;
     sem_wait(sem_);
   }
 
@@ -51,48 +50,64 @@ struct PlatformScopedMutexLockLinux : public PlatformScopedMutexLock {
   }
 };
 
+void* checked(void* result, const char* expr) {
+  if (!result) {
+    std::cerr << "FAIL errno=" << errno << " in |" << expr << "|" << std::endl;
+    exit(1);
+  }
+  return result;
+}
+
+int checked(int result, const char* expr) {
+  if (result == -1) {
+    std::cerr << "FAIL errno=" << errno << " in |" << expr << "|" << std::endl;
+    exit(1);
+  }
+  return result;
+}
+
+#define CHECKED(expr) checked(expr, #expr)
+
 struct PlatformSharedMemoryLinux : public PlatformSharedMemory {
   std::string name_;
   int fd_;
 
   PlatformSharedMemoryLinux(const std::string& name) : name_(name) {
-    std::cout << "PlatformSharedMemoryLinux name=" << name << std::endl;
-    fd_ = shm_open(name_.c_str(), O_CREAT, O_RDWR);
-    std::cout << "shm_open errno=" << errno << std::endl;
-    std::cout << "1" << std::endl;
-    ftruncate(fd_, shmem_size);
-    std::cout << "ftruncate errno=" << errno << std::endl;
-    std::cout << "2" << std::endl;
+    std::cerr << "PlatformSharedMemoryLinux name=" << name << std::endl;
 
-   //void *mmap(void *addr, size_t length, int prot, int flags,
-   //           int fd, off_t offset);
-   //int munmap(void *addr, size_t length);
-   //
-    //shmem_size
-    std::cout << "3" << std::endl;
-    shared = mmap(nullptr /*kernel assigned starting address*/,
-         shmem_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0 /*offset*/);
-    std::cout << "mmap errno=" << errno << std::endl;
-    std::cout << "fd_ = " << fd_ << std::endl;
-    std::cout << "shared = " << shared << std::endl;
-    std::cout << "4" << std::endl;
+    // Try to create shared memory but only if it does not already exist. Since
+    // we created the memory, we need to initialize it.
+    fd_ = shm_open(name_.c_str(), O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+    if (fd_ >= 0) {
+      std::cerr << "Calling ftruncate fd_=" << fd_ << std::endl;
+      CHECKED(ftruncate(fd_, shmem_size));
+    }
 
-    /*
-      int fd = shm_open("shmname", O_CREAT, O_RDWR);
-      sem_t *sem = mmap(NULL, sizeof(sem_t), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
-      ftruncate(fd_, shmem_size);
+    // Otherwise, we just open existing shared memory. We don't need to
+    // create or initialize it.
+    else {
+      fd_ = CHECKED(shm_open(name_.c_str(),
+                             O_RDWR, /* memory is read/write, create if needed */
+                             S_IRUSR | S_IWUSR /* user read/write */));
+    }
 
-      sem_init(sem, 1, 1);
-     */
+    // Map the shared memory to an address.
+    shared = CHECKED(mmap(nullptr /*kernel assigned starting address*/,
+                          shmem_size, PROT_READ | PROT_WRITE, MAP_SHARED,
+                          fd_, 0 /*offset*/));
+
+    std::cout << "Open shared memory name=" << name << ", fd=" << fd_ << ", shared=" << shared << std::endl;
   }
 
   ~PlatformSharedMemoryLinux() override {
-    munmap(shared, shmem_size);
+    CHECKED(munmap(shared, shmem_size));
+    CHECKED(shm_unlink(name_.c_str()));
+
     shared = nullptr;
-    shm_unlink(name_.c_str());
   }
 };
 
+#undef CHECKED
 
 
 std::unique_ptr<PlatformMutex> CreatePlatformMutex(const std::string& name) {