PR28417, std::string no longer allows accepting nullptr_t

[Alan Modra]

	PR 28417
	* incremental.cc (Sized_relobj_incr::do_section_name): Avoid
	std:string undefined behaviour.
	* options.h (Search_directory::Search_directory): Likewise.

diff --git a/gold/incremental.cc b/gold/incremental.cc
index 52941985e6f..327a1527a29 100644
--- a/gold/incremental.cc
+++ b/gold/incremental.cc
@@ -2286,7 +2286,7 @@ Sized_relobj_incr<size, big_endian>::do_section_name(unsigned int shndx) const
   const Output_sections& out_sections(this->output_sections());
   const Output_section* os = out_sections[shndx];
   if (os == NULL)
-    return NULL;
+    return std::string();
   return os->name();
 }
 
diff --git a/gold/options.h b/gold/options.h
index 757ebf18fec..47299a37834 100644
--- a/gold/options.h
+++ b/gold/options.h
@@ -611,7 +611,7 @@ class Search_directory
   // We need a default constructor because we put this in a
   // std::vector.
   Search_directory()
-    : name_(NULL), put_in_sysroot_(false), is_in_sysroot_(false)
+    : name_(), put_in_sysroot_(false), is_in_sysroot_(false)
   { }
 
   // This is the usual constructor.

-- 
Alan Modra
Australia Development Lab, IBM