diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_libcdep.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_libcdep.cpp
--- a/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_libcdep.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_libcdep.cpp
@@ -39,9 +39,9 @@
 }
 
 const char *ExtractInt(const char *str, const char *delims, int *result) {
-  char *buff;
+  char *buff = nullptr;
   const char *ret = ExtractToken(str, delims, &buff);
-  if (buff != 0) {
+  if (buff) {
     *result = (int)internal_atoll(buff);
   }
   InternalFree(buff);
@@ -49,9 +49,9 @@
 }
 
 const char *ExtractUptr(const char *str, const char *delims, uptr *result) {
-  char *buff;
+  char *buff = nullptr;
   const char *ret = ExtractToken(str, delims, &buff);
-  if (buff != 0) {
+  if (buff) {
     *result = (uptr)internal_atoll(buff);
   }
   InternalFree(buff);
@@ -59,9 +59,9 @@
 }
 
 const char *ExtractSptr(const char *str, const char *delims, sptr *result) {
-  char *buff;
+  char *buff = nullptr;
   const char *ret = ExtractToken(str, delims, &buff);
-  if (buff != 0) {
+  if (buff) {
     *result = (sptr)internal_atoll(buff);
   }
   InternalFree(buff);
@@ -83,7 +83,7 @@
 
 SymbolizedStack *Symbolizer::SymbolizePC(uptr addr) {
   BlockingMutexLock l(&mu_);
-  const char *module_name;
+  const char *module_name = nullptr;
   uptr module_offset;
   ModuleArch arch;
   SymbolizedStack *res = SymbolizedStack::New(addr);
@@ -103,7 +103,7 @@
 
 bool Symbolizer::SymbolizeData(uptr addr, DataInfo *info) {
   BlockingMutexLock l(&mu_);
-  const char *module_name;
+  const char *module_name = nullptr;
   uptr module_offset;
   ModuleArch arch;
   if (!FindModuleNameAndOffsetForAddress(addr, &module_name, &module_offset,
@@ -124,7 +124,7 @@
 
 bool Symbolizer::SymbolizeFrame(uptr addr, FrameInfo *info) {
   BlockingMutexLock l(&mu_);
-  const char *module_name;
+  const char *module_name = nullptr;
   if (!FindModuleNameAndOffsetForAddress(
           addr, &module_name, &info->module_offset, &info->module_arch))
     return false;
@@ -175,7 +175,7 @@
                                                    uptr *module_offset,
                                                    ModuleArch *module_arch) {
   const LoadedModule *module = FindModuleForAddress(address);
-  if (module == nullptr)
+  if (!module)
     return false;
   *module_name = module->full_name();
   *module_offset = address - module->base_address();
@@ -292,7 +292,7 @@
 // Windows, so extract tokens from the right hand side first. The column info is
 // also optional.
 static const char *ParseFileLineInfo(AddressInfo *info, const char *str) {
-  char *file_line_info = 0;
+  char *file_line_info = nullptr;
   str = ExtractToken(str, "\n", &file_line_info);
   CHECK(file_line_info);
 
@@ -323,7 +323,7 @@
   bool top_frame = true;
   SymbolizedStack *last = res;
   while (true) {
-    char *function_name = 0;
+    char *function_name = nullptr;
     str = ExtractToken(str, "\n", &function_name);
     CHECK(function_name);
     if (function_name[0] == '\0') {
@@ -402,32 +402,29 @@
   AddressInfo *info = &stack->info;
   const char *buf = FormatAndSendCommand(
       "CODE", info->module, info->module_offset, info->module_arch);
-  if (buf) {
-    ParseSymbolizePCOutput(buf, stack);
-    return true;
-  }
-  return false;
+  if (!buf)
+    return false;
+  ParseSymbolizePCOutput(buf, stack);
+  return true;
 }
 
 bool LLVMSymbolizer::SymbolizeData(uptr addr, DataInfo *info) {
   const char *buf = FormatAndSendCommand(
       "DATA", info->module, info->module_offset, info->module_arch);
-  if (buf) {
-    ParseSymbolizeDataOutput(buf, info);
-    info->start += (addr - info->module_offset); // Add the base address.
-    return true;
-  }
-  return false;
+  if (!buf)
+    return false;
+  ParseSymbolizeDataOutput(buf, info);
+  info->start += (addr - info->module_offset); // Add the base address.
+  return true;
 }
 
 bool LLVMSymbolizer::SymbolizeFrame(uptr addr, FrameInfo *info) {
   const char *buf = FormatAndSendCommand(
       "FRAME", info->module, info->module_offset, info->module_arch);
-  if (buf) {
-    ParseSymbolizeFrameOutput(buf, &info->locals);
-    return true;
-  }
-  return false;
+  if (!buf)
+    return false;
+  ParseSymbolizeFrameOutput(buf, &info->locals);
+  return true;
 }
 
 const char *LLVMSymbolizer::FormatAndSendCommand(const char *command_prefix,
@@ -435,21 +432,21 @@
                                                  uptr module_offset,
                                                  ModuleArch arch) {
   CHECK(module_name);
-  if (arch == kModuleArchUnknown) {
-    if (internal_snprintf(buffer_, kBufferSize, "%s \"%s\" 0x%zx\n",
-                          command_prefix, module_name,
-                          module_offset) >= static_cast<int>(kBufferSize)) {
-      Report("WARNING: Command buffer too small");
-      return nullptr;
-    }
-  } else {
-    if (internal_snprintf(buffer_, kBufferSize, "%s \"%s:%s\" 0x%zx\n",
-                          command_prefix, module_name, ModuleArchToString(arch),
-                          module_offset) >= static_cast<int>(kBufferSize)) {
-      Report("WARNING: Command buffer too small");
-      return nullptr;
-    }
+  int size_needed = 0;
+  if (arch == kModuleArchUnknown)
+    size_needed = internal_snprintf(buffer_, kBufferSize, "%s \"%s\" 0x%zx\n",
+                                    command_prefix, module_name, module_offset);
+  else
+    size_needed = internal_snprintf(buffer_, kBufferSize,
+                                    "%s \"%s:%s\" 0x%zx\n", command_prefix,
+                                    module_name, ModuleArchToString(arch),
+                                    module_offset);
+
+  if (size_needed >= static_cast<int>(kBufferSize)) {
+    Report("WARNING: Command buffer too small");
+    return nullptr;
   }
+
   return symbolizer_process_->SendCommand(buffer_);
 }
 
@@ -492,16 +489,16 @@
     Report("WARNING: Failed to use and restart external symbolizer!\n");
     failed_to_start_ = true;
   }
-  return 0;
+  return nullptr;
 }
 
 const char *SymbolizerProcess::SendCommandImpl(const char *command) {
   if (input_fd_ == kInvalidFd || output_fd_ == kInvalidFd)
-      return 0;
+      return nullptr;
   if (!WriteToSymbolizer(command, internal_strlen(command)))
-      return 0;
+      return nullptr;
   if (!ReadFromSymbolizer(buffer_, kBufferSize))
-      return 0;
+      return nullptr;
   return buffer_;
 }
 
@@ -532,8 +529,8 @@
       break;
     if (read_len + 1 == max_length) {
       Report("WARNING: Symbolizer buffer too small\n");
-      read_len = 0;
-      break;
+      buffer[0] = '\0';
+      return false;
     }
   }
   buffer[read_len] = '\0';