gdb: merge debug symbol file lookup code from coffread & elfread paths

This commit merges the code that looks for and loads the separate
debug symbol files from coffread.c and elfread.c.  The factored out
code is moved into a new objfile::find_and_add_separate_symbol_file()
method.

For the elfread.c path there should be no user visible changes after
this commit.

For the coffread.c path GDB will now attempt to perform a debuginfod
lookup for the missing debug information, assuming that GDB can find a
build-id in the COFF file.

I don't know if COFF files can include a build-id, but I the existing
coffread.c code already includes a call to
find_separate_debug_file_by_build-id, so I know that it is at least OK
for GDB to ask a COFF file for a build-id.  If the COFF file doesn't
include a build-id then the debuginfod lookup code will not trigger
and the new code is harmless.

If the COFF file does include a build-id, then we're going to end up
asking debuginfod for the debug file.  As build-ids should be unique,
this should be harmless, even if debuginfod doesn't contain any
suitable debug data, it just costs us one debuginfod lookup, so I'm
not too worried about this for now.

As with the previous commit, I've done some minimal testing using the
mingw toolchain on a Linux machine, GDB seems to still access the
split debug information just fine.

Approved-By: Tom Tromey <tom@tromey.com>

4 files changed, 81 insertions, 76 deletions

diff --git a/gdb/coffread.c b/gdb/coffread.c
index e1415d6..5898b3a 100644
--- a/gdb/coffread.c
+++ b/gdb/coffread.c
@@ -40,8 +40,6 @@
 
 #include "coff-pe-read.h"
 
-#include "build-id.h"
-
 /* The objfile we are currently reading.  */
 
 static struct objfile *coffread_objfile;
@@ -729,26 +727,8 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
 	   && objfile->separate_debug_objfile == NULL
 	   && objfile->separate_debug_objfile_backlink == NULL)
     {
-      deferred_warnings warnings;
-      std::string debugfile
-	= find_separate_debug_file_by_buildid (objfile, &warnings);
-
-      if (debugfile.empty ())
-	debugfile
-	  = find_separate_debug_file_by_debuglink (objfile, &warnings);
-
-      if (!debugfile.empty ())
-	{
-	  gdb_bfd_ref_ptr debug_bfd (symfile_bfd_open (debugfile.c_str ()));
-
-	  symbol_file_add_separate (debug_bfd, debugfile.c_str (),
-				    symfile_flags, objfile);
-	}
-      /* If all the methods to collect the debuginfo failed, print any
-	 warnings that were collected, this is a no-op if there are no
-	 warnings.  */
-      if (debugfile.empty ())
-	warnings.emit ();
+      if (objfile->find_and_add_separate_symbol_file (symfile_flags))
+	gdb_assert (objfile->separate_debug_objfile != nullptr);
     }
 }
 
diff --git a/gdb/elfread.c b/gdb/elfread.c
index 7900dfb..86e7f61 100644
--- a/gdb/elfread.c
+++ b/gdb/elfread.c
@@ -41,14 +41,12 @@
 #include "regcache.h"
 #include "bcache.h"
 #include "gdb_bfd.h"
-#include "build-id.h"
 #include "location.h"
 #include "auxv.h"
 #include "mdebugread.h"
 #include "ctfread.h"
 #include "gdbsupport/gdb_string_view.h"
 #include "gdbsupport/scoped_fd.h"
-#include "debuginfod-support.h"
 #include "dwarf2/public.h"
 #include "cli/cli-cmds.h"
 
@@ -1218,59 +1216,10 @@ elf_symfile_read_dwarf2 (struct objfile *objfile,
 	   && objfile->separate_debug_objfile == NULL
 	   && objfile->separate_debug_objfile_backlink == NULL)
     {
-      deferred_warnings warnings;
-
-      std::string debugfile
-	= find_separate_debug_file_by_buildid (objfile, &warnings);
-
-      if (debugfile.empty ())
-	debugfile = find_separate_debug_file_by_debuglink (objfile, &warnings);
-
-      if (!debugfile.empty ())
-	{
-	  gdb_bfd_ref_ptr debug_bfd
-	    (symfile_bfd_open_no_error (debugfile.c_str ()));
-
-	  if (debug_bfd != nullptr)
-	    symbol_file_add_separate (debug_bfd, debugfile.c_str (),
-				      symfile_flags, objfile);
-	}
+      if (objfile->find_and_add_separate_symbol_file (symfile_flags))
+	gdb_assert (objfile->separate_debug_objfile != nullptr);
       else
-	{
-	  has_dwarf2 = false;
-	  const struct bfd_build_id *build_id
-	    = build_id_bfd_get (objfile->obfd.get ());
-	  const char *filename = bfd_get_filename (objfile->obfd.get ());
-
-	  if (build_id != nullptr)
-	    {
-	      gdb::unique_xmalloc_ptr<char> symfile_path;
-	      scoped_fd fd (debuginfod_debuginfo_query (build_id->data,
-							build_id->size,
-							filename,
-							&symfile_path));
-
-	      if (fd.get () >= 0)
-		{
-		  /* File successfully retrieved from server.  */
-		  gdb_bfd_ref_ptr debug_bfd
-		    (symfile_bfd_open_no_error (symfile_path.get ()));
-
-		  if (debug_bfd != nullptr
-		      && build_id_verify (debug_bfd.get (), build_id->size,
-					  build_id->data))
-		    {
-		      symbol_file_add_separate (debug_bfd, symfile_path.get (),
-						symfile_flags, objfile);
-		      has_dwarf2 = true;
-		    }
-		}
-	    }
-	}
-      /* If all the methods to collect the debuginfo failed, print the
-	 warnings, this is a no-op if there are no warnings.  */
-      if (debugfile.empty () && !has_dwarf2)
-	warnings.emit ();
+	has_dwarf2 = false;
     }
 
   return has_dwarf2;
diff --git a/gdb/objfiles.h b/gdb/objfiles.h
index 4b8aa9b..ec9d354 100644
--- a/gdb/objfiles.h
+++ b/gdb/objfiles.h
@@ -513,6 +513,16 @@ public:
 
   bool has_partial_symbols ();
 
+  /* Look for a separate debug symbol file for this objfile, make use of
+     build-id, debug-link, and debuginfod as necessary.  If a suitable
+     separate debug symbol file is found then it is loaded using a call to
+     symbol_file_add_separate (SYMFILE_FLAGS is passed through unmodified
+     to this call) and this function returns true.  If no suitable separate
+     debug symbol file is found and loaded then this function returns
+     false.  */
+
+  bool find_and_add_separate_symbol_file (symfile_add_flags symfile_flags);
+
   /* Return true if this objfile has any unexpanded symbols.  A return
      value of false indicates either, that this objfile has all its
      symbols fully expanded (i.e. fully read in), or that this objfile has
diff --git a/gdb/symfile-debug.c b/gdb/symfile-debug.c
index 850da41..961ae23 100644
--- a/gdb/symfile-debug.c
+++ b/gdb/symfile-debug.c
@@ -35,6 +35,8 @@
 #include "block.h"
 #include "filenames.h"
 #include "cli/cli-style.h"
+#include "build-id.h"
+#include "debuginfod-support.h"
 
 /* We need to save a pointer to the real symbol functions.
    Plus, the debug versions are malloc'd because we have to NULL out the
@@ -558,6 +560,70 @@ objfile::require_partial_symbols (bool verbose)
     }
 }
 
+/* See objfiles.h.  */
+
+bool
+objfile::find_and_add_separate_symbol_file (symfile_add_flags symfile_flags)
+{
+  bool has_dwarf2 = true;
+
+  deferred_warnings warnings;
+
+  std::string debugfile
+    = find_separate_debug_file_by_buildid (this, &warnings);
+
+  if (debugfile.empty ())
+    debugfile = find_separate_debug_file_by_debuglink (this, &warnings);
+
+  if (!debugfile.empty ())
+    {
+      gdb_bfd_ref_ptr debug_bfd
+	(symfile_bfd_open_no_error (debugfile.c_str ()));
+
+      if (debug_bfd != nullptr)
+	symbol_file_add_separate (debug_bfd, debugfile.c_str (),
+				  symfile_flags, this);
+    }
+  else
+    {
+      has_dwarf2 = false;
+      const struct bfd_build_id *build_id
+	= build_id_bfd_get (this->obfd.get ());
+      const char *filename = bfd_get_filename (this->obfd.get ());
+
+      if (build_id != nullptr)
+	{
+	  gdb::unique_xmalloc_ptr<char> symfile_path;
+	  scoped_fd fd (debuginfod_debuginfo_query (build_id->data,
+						    build_id->size,
+						    filename,
+						    &symfile_path));
+
+	  if (fd.get () >= 0)
+	    {
+	      /* File successfully retrieved from server.  */
+	      gdb_bfd_ref_ptr debug_bfd
+		(symfile_bfd_open_no_error (symfile_path.get ()));
+
+	      if (debug_bfd != nullptr
+		  && build_id_verify (debug_bfd.get (), build_id->size,
+				      build_id->data))
+		{
+		  symbol_file_add_separate (debug_bfd, symfile_path.get (),
+					    symfile_flags, this);
+		  has_dwarf2 = true;
+		}
+	    }
+	}
+    }
+  /* If all the methods to collect the debuginfo failed, print the
+     warnings, this is a no-op if there are no warnings.  */
+  if (debugfile.empty () && !has_dwarf2)
+    warnings.emit ();
+
+  return has_dwarf2;
+}
+
 
 /* Debugging version of struct sym_probe_fns.  */