win: Don't attempt to read a nonexistent IMAGE_DIRECTORY_ENTRY_DEBUG

snapshot/win/pe_image_reader.h

Index: snapshot/win/pe_image_reader.h
diff --git a/snapshot/win/pe_image_reader.h b/snapshot/win/pe_image_reader.h
index 73a9e3823b30315796c706f626b333daf2e87cb2..b950a8c956cc15682c0f6cece940b7a18f5ac17e 100644
--- a/snapshot/win/pe_image_reader.h
+++ b/snapshot/win/pe_image_reader.h
@@ -109,14 +109,29 @@ class PEImageReader {
  private:
   //! \brief Implementation helper for DebugDirectoryInformation() templated by
   //!     `IMAGE_NT_HEADERS` type for different bitnesses.
+  //!
+  //! \return `true` on success, with the parameters set appropriately. `false`
+  //!     on failure. This method may return `false` without logging anything in
+  //!     the case of a module that does not contain relevant debugging
+  //!     information but is otherwise properly structured.
   template <class NtHeadersType>
   bool ReadDebugDirectoryInformation(UUID* uuid,
                                      DWORD* age,
                                      std::string* pdbname) const;
 
   //! \brief Reads the `IMAGE_NT_HEADERS` from the beginning of the image.
+  //!
+  //! \param[out] nt_headers_address The address of the templated NtHeadersType
+  //!     structure in the remote process’ address space. If this information is
+  //!     not needed, this parameter may be `nullptr`.
+  //! \param[out] nt_headers The contents of the templated NtHeadersType
+  //!     structure read from the remote process.
+  //!
+  //! \return `true` on success, with \a nt_headers and optionally \a
+  //!     nt_headers_address set appropriately. `false` on failure, with a
+  //!     message logged.
   template <class NtHeadersType>
-  bool ReadNtHeaders(WinVMAddress* nt_header_address,
+  bool ReadNtHeaders(WinVMAddress* nt_headers_address,

[scottmg, 2015/10/28 19:55:11]

Maybe it'd be nice to swap the order of these arguments to make the optional one
last.

                      NtHeadersType* nt_headers) const;
 
   //! \brief Finds a given section by name in the image.