gdb: style filenames in separate debug file warnings

After the commit:

  commit 6647f05df023b63bbe056e9167e9e234172fa2ca
  Date:   Tue Jan 24 18:13:38 2023 +0100

      gdb: defer warnings when loading separate debug files

It was pointed out[1] that the warnings being deferred and then later
emitted lacked styling.  The warnings lacked styling before the above
commit, but it was suggested that the filenames in these warnings
should be styled, and this commit does this.

There were a couple of previous attempts[2][3][4] to solve this
problem, but these all tried to extend the mechanism introduced in the
above commit, the deferred warnings were placed directly into a
std::vector, but now we tried to, when appropriate, style these
warnings.  The review feedback that this approach looked too complex.

So instead, this revision adds a new helper class 'deferred_warnings'
which can be used to collect a set of deferred warnings, and then emit
these deferred warnings later, if needed.  This helper class hides the
complexity, so at the point the deferred warning is created no extra
logic is required.

The deferred_warnings class will style the deferred warnings only if
gdb_stderr supports styling.  GDB's warnings are sent to gdb_stderr,
so this should ensure we only style when expected.

There was also review feedback[5] that all of the warnings should be
bundled into a single string_file, this has not been done.  I feel
pretty strongly that separate warnings should be emitted using
separate "warning" calls.  If we do end up with multiple warnings in
this case they aren't really related, one will be about looking up
debug via .gnu_debuglink, while the other will be about build-id based
lookup.  So I'd really rather keep the warnings separate.

[1] https://inbox.sourceware.org/gdb-patches/87edr9pcku.fsf@tromey.com/
[2] https://inbox.sourceware.org/gdb-patches/20230216195604.2685177-1-ahajkova@redhat.com/
[3] https://inbox.sourceware.org/gdb-patches/20230217123547.2737612-1-ahajkova@redhat.com/
[4] https://inbox.sourceware.org/gdb-patches/20230320145638.1202335-1-ahajkova@redhat.com/
[5] https://inbox.sourceware.org/gdb-patches/87o7nh1g8h.fsf@tromey.com/

Co-Authored-By: Alexandra Hájková <ahajkova@redhat.com>
Approved-By: Simon Marchi <simon.marchi@efficios.com>

11 files changed, 167 insertions, 53 deletions

diff --git a/gdb/build-id.c b/gdb/build-id.c
index 65b493f..f68384f 100644
--- a/gdb/build-id.c
+++ b/gdb/build-id.c
@@ -26,6 +26,7 @@
 #include "objfiles.h"
 #include "filenames.h"
 #include "gdbcore.h"
+#include "cli/cli-style.h"
 
 /* See build-id.h.  */
 
@@ -209,7 +210,7 @@ build_id_to_exec_bfd (size_t build_id_len, const bfd_byte *build_id)
 
 std::string
 find_separate_debug_file_by_buildid (struct objfile *objfile,
-				     std::vector<std::string> *warnings_vector)
+				     deferred_warnings *warnings)
 {
   const struct bfd_build_id *build_id;
 
@@ -228,12 +229,13 @@ find_separate_debug_file_by_buildid (struct objfile *objfile,
 	  && filename_cmp (bfd_get_filename (abfd.get ()),
 			   objfile_name (objfile)) == 0)
 	{
-	  std::string msg
-	    = string_printf (_("\"%s\": separate debug info file has no "
-			       "debug info"), bfd_get_filename (abfd.get ()));
 	  if (separate_debug_file_debug)
-	    gdb_printf (gdb_stdlog, "%s", msg.c_str ());
-	  warnings_vector->emplace_back (std::move (msg));
+	    gdb_printf (gdb_stdlog, "\"%s\": separate debug info file has no "
+			"debug info", bfd_get_filename (abfd.get ()));
+	  warnings->warn (_("\"%ps\": separate debug info file has no "
+			    "debug info"),
+			  styled_string (file_name_style.style (),
+					 bfd_get_filename (abfd.get ())));
 	}
       else if (abfd != NULL)
 	return std::string (bfd_get_filename (abfd.get ()));
diff --git a/gdb/build-id.h b/gdb/build-id.h
index 191720d..a5c8b85 100644
--- a/gdb/build-id.h
+++ b/gdb/build-id.h
@@ -52,13 +52,13 @@ extern gdb_bfd_ref_ptr build_id_to_exec_bfd (size_t build_id_len,
    separate debug file, otherwise, return an empty string.
 
    Any warnings that are generated by the lookup process should be added to
-   WARNINGS_VECTOR, one std::string per warning.  If some other mechanism can
-   be used to lookup the debug information then the warning will not be shown,
-   however, if GDB fails to find suitable debug information using any
-   approach, then any warnings will be printed.  */
+   WARNINGS.  If some other mechanism can be used to lookup the debug
+   information then the warning will not be shown, however, if GDB fails to
+   find suitable debug information using any approach, then any warnings
+   will be printed.  */
 
 extern std::string find_separate_debug_file_by_buildid
-  (struct objfile *objfile, std::vector<std::string> *warnings_vector);
+  (struct objfile *objfile, deferred_warnings *warnings);
 
 /* Return an hex-string representation of BUILD_ID.  */
 
diff --git a/gdb/coffread.c b/gdb/coffread.c
index ff4d4ae..33fb2ba 100644
--- a/gdb/coffread.c
+++ b/gdb/coffread.c
@@ -729,13 +729,13 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
   /* Try to add separate debug file if no symbols table found.   */
   if (!objfile->has_partial_symbols ())
     {
-      std::vector<std::string> warnings_vector;
+      deferred_warnings warnings;
       std::string debugfile
-	= find_separate_debug_file_by_buildid (objfile, &warnings_vector);
+	= find_separate_debug_file_by_buildid (objfile, &warnings);
 
       if (debugfile.empty ())
 	debugfile
-	  = find_separate_debug_file_by_debuglink (objfile, &warnings_vector);
+	  = find_separate_debug_file_by_debuglink (objfile, &warnings);
 
       if (!debugfile.empty ())
 	{
@@ -745,10 +745,10 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
 				    symfile_flags, objfile);
 	}
       /* If all the methods to collect the debuginfo failed, print any
-	 warnings that were collected.  */
-      if (debugfile.empty () && !warnings_vector.empty ())
-	for (const std::string &w : warnings_vector)
-	  warning ("%s", w.c_str ());
+	 warnings that were collected, this is a no-op if there are no
+	 warnings.  */
+      if (debugfile.empty ())
+	warnings.emit ();
     }
 }
 
diff --git a/gdb/disasm.h b/gdb/disasm.h
index 7e1bb8d..dbc63e5 100644
--- a/gdb/disasm.h
+++ b/gdb/disasm.h
@@ -150,7 +150,7 @@ protected:
      DIS_INFO pointer is a pointer to a gdb_printing_disassembler object.
      Content is written to the m_stream extracted from DIS_INFO.  */
   static int fprintf_func (void *dis_info, const char *format, ...) noexcept
-    ATTRIBUTE_PRINTF(2,3);
+    ATTRIBUTE_PRINTF (2, 3);
 
   /* Callback used as the disassemble_info's fprintf_styled_func callback.
      The DIS_INFO pointer is a pointer to a gdb_printing_disassembler
diff --git a/gdb/elfread.c b/gdb/elfread.c
index 7697106..349a8b7 100644
--- a/gdb/elfread.c
+++ b/gdb/elfread.c
@@ -1225,14 +1225,13 @@ elf_symfile_read_dwarf2 (struct objfile *objfile,
 	   && objfile->separate_debug_objfile == NULL
 	   && objfile->separate_debug_objfile_backlink == NULL)
     {
-      std::vector<std::string> warnings_vector;
+      deferred_warnings warnings;
 
       std::string debugfile
-	= find_separate_debug_file_by_buildid (objfile, &warnings_vector);
+	= find_separate_debug_file_by_buildid (objfile, &warnings);
 
       if (debugfile.empty ())
-	debugfile = find_separate_debug_file_by_debuglink (objfile,
-							   &warnings_vector);
+	debugfile = find_separate_debug_file_by_debuglink (objfile, &warnings);
 
       if (!debugfile.empty ())
 	{
@@ -1275,11 +1274,10 @@ elf_symfile_read_dwarf2 (struct objfile *objfile,
 		}
 	    }
 	}
-      /* If all the methods to collect the debuginfo failed, print
-	 the warnings, if there're any. */
-      if (debugfile.empty () && !has_dwarf2 && !warnings_vector.empty ())
-	for (const std::string &w : warnings_vector)
-	  warning ("%s", w.c_str ());
+      /* 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;
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 3a0aee1..d284040 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -1243,7 +1243,7 @@ bool separate_debug_file_debug = false;
 static int
 separate_debug_file_exists (const std::string &name, unsigned long crc,
 			    struct objfile *parent_objfile,
-			    std::vector<std::string> *warnings_vector)
+			    deferred_warnings *warnings)
 {
   unsigned long file_crc;
   int file_crc_p;
@@ -1336,13 +1336,16 @@ separate_debug_file_exists (const std::string &name, unsigned long crc,
 
       if (verified_as_different || parent_crc != file_crc)
 	{
-	  std::string msg
-	    = string_printf (_("the debug information found in \"%s\""
-			       " does not match \"%s\" (CRC mismatch).\n"),
-			     name.c_str (), objfile_name (parent_objfile));
 	  if (separate_debug_file_debug)
-	    gdb_printf (gdb_stdlog, "%s", msg.c_str ());
-	  warnings_vector->emplace_back (std::move (msg));
+	    gdb_printf (gdb_stdlog, "the debug information found in \"%s\""
+			" does not match \"%s\" (CRC mismatch).\n",
+			name.c_str (), objfile_name (parent_objfile));
+	  warnings->warn (_("the debug information found in \"%ps\""
+			    " does not match \"%ps\" (CRC mismatch)."),
+			  styled_string (file_name_style.style (),
+					 name.c_str ()),
+			  styled_string (file_name_style.style (),
+					 objfile_name (parent_objfile)));
 	}
 
       return 0;
@@ -1378,14 +1381,17 @@ show_debug_file_directory (struct ui_file *file, int from_tty,
    string.
 
    Any warnings generated as part of the lookup process are added to
-   WARNINGS_VECTOR, one std::string per warning.  */
+   WARNINGS.  If some other mechanism can be used to lookup the debug
+   information then the warning will not be shown, however, if GDB fails to
+   find suitable debug information using any approach, then any warnings
+   will be printed.  */
 
 static std::string
 find_separate_debug_file (const char *dir,
 			  const char *canon_dir,
 			  const char *debuglink,
 			  unsigned long crc32, struct objfile *objfile,
-			  std::vector<std::string> *warnings_vector)
+			  deferred_warnings *warnings)
 {
   if (separate_debug_file_debug)
     gdb_printf (gdb_stdlog,
@@ -1396,7 +1402,7 @@ find_separate_debug_file (const char *dir,
   std::string debugfile = dir;
   debugfile += debuglink;
 
-  if (separate_debug_file_exists (debugfile, crc32, objfile, warnings_vector))
+  if (separate_debug_file_exists (debugfile, crc32, objfile, warnings))
     return debugfile;
 
   /* Then try in the subdirectory named DEBUG_SUBDIRECTORY.  */
@@ -1405,7 +1411,7 @@ find_separate_debug_file (const char *dir,
   debugfile += "/";
   debugfile += debuglink;
 
-  if (separate_debug_file_exists (debugfile, crc32, objfile, warnings_vector))
+  if (separate_debug_file_exists (debugfile, crc32, objfile, warnings))
     return debugfile;
 
   /* Then try in the global debugfile directories.
@@ -1450,8 +1456,7 @@ find_separate_debug_file (const char *dir,
       debugfile += dir_notarget;
       debugfile += debuglink;
 
-      if (separate_debug_file_exists (debugfile, crc32, objfile,
-				      warnings_vector))
+      if (separate_debug_file_exists (debugfile, crc32, objfile, warnings))
 	return debugfile;
 
       const char *base_path = NULL;
@@ -1473,8 +1478,7 @@ find_separate_debug_file (const char *dir,
 	  debugfile += "/";
 	  debugfile += debuglink;
 
-	  if (separate_debug_file_exists (debugfile, crc32, objfile,
-					  warnings_vector))
+	  if (separate_debug_file_exists (debugfile, crc32, objfile, warnings))
 	    return debugfile;
 
 	  /* If the file is in the sysroot, try using its base path in
@@ -1501,7 +1505,7 @@ find_separate_debug_file (const char *dir,
 	      debugfile += debuglink;
 
 	      if (separate_debug_file_exists (debugfile, crc32, objfile,
-					      warnings_vector))
+					      warnings))
 		return debugfile;
 	    }
 	}
@@ -1533,7 +1537,7 @@ terminate_after_last_dir_separator (char *path)
 
 std::string
 find_separate_debug_file_by_debuglink
-  (struct objfile *objfile, std::vector<std::string> *warnings_vector)
+  (struct objfile *objfile, deferred_warnings *warnings)
 {
   uint32_t crc32;
 
@@ -1554,7 +1558,7 @@ find_separate_debug_file_by_debuglink
   std::string debugfile
     = find_separate_debug_file (dir.c_str (), canon_dir.get (),
 				debuglink.get (), crc32, objfile,
-				warnings_vector);
+				warnings);
 
   if (debugfile.empty ())
     {
@@ -1579,7 +1583,7 @@ find_separate_debug_file_by_debuglink
 							debuglink.get (),
 							crc32,
 							objfile,
-							warnings_vector);
+							warnings);
 		}
 	    }
 	}
diff --git a/gdb/symfile.h b/gdb/symfile.h
index 7c800ea..296fee9 100644
--- a/gdb/symfile.h
+++ b/gdb/symfile.h
@@ -244,11 +244,14 @@ extern void symbol_file_add_separate (const gdb_bfd_ref_ptr &, const char *,
 /* Find separate debuginfo for OBJFILE (using .gnu_debuglink section).
    Returns pathname, or an empty string.
 
-   Any warnings generated as part of this lookup are added to
-   WARNINGS_VECTOR, one std::string per warning.  */
+   Any warnings generated as part of this lookup are added to WARNINGS.  If
+   some other mechanism can be used to lookup the debug information then
+   the warning will not be shown, however, if GDB fails to find suitable
+   debug information using any approach, then any warnings will be
+   printed.  */
 
 extern std::string find_separate_debug_file_by_debuglink
-  (struct objfile *objfile, std::vector<std::string> *warnings_vector);
+  (struct objfile *objfile, deferred_warnings *warnings);
 
 /* Build (allocate and populate) a section_addr_info struct from an
    existing section table.  */
diff --git a/gdb/testsuite/gdb.debuginfod/build-id-no-debug-warning.exp b/gdb/testsuite/gdb.debuginfod/build-id-no-debug-warning.exp
index b49770f..148363a 100644
--- a/gdb/testsuite/gdb.debuginfod/build-id-no-debug-warning.exp
+++ b/gdb/testsuite/gdb.debuginfod/build-id-no-debug-warning.exp
@@ -95,6 +95,30 @@ gdb_test "file ${build_id_debug_file}" \
 	 "\\(No debugging symbols found in \[^\r\n\]+\\)"] \
     "load test file, expect a warning"
 
+# Do the same thing again, but this time check that the styling is
+# correct.
+with_test_prefix "check styling" {
+    save_vars { env(TERM) } {
+	# We need an ANSI-capable terminal to get styled output.
+	setenv TERM ansi
+
+	clean_restart
+
+	gdb_test_no_output "set debug-file-directory ${debug_file_directory}" \
+	    "set debug-file-directory"
+
+	# Now load the file into GDB, and look for the warning.
+	set debug_file_re [style [string_to_regexp $build_id_debug_file] file]
+
+	gdb_test "file ${build_id_debug_file}" \
+	    [multi_line \
+		 "Reading symbols from $debug_file_re\\.\\.\\." \
+		 "warning: \"$debug_file_re\": separate debug info file has no debug info" \
+		 "\\(No debugging symbols found in \[^\r\n\]+\\)"] \
+	    "load test file, expect a warning"
+    }
+}
+
 # Now we should close GDB.
 gdb_exit
 
diff --git a/gdb/testsuite/gdb.debuginfod/crc_mismatch.exp b/gdb/testsuite/gdb.debuginfod/crc_mismatch.exp
index 588fb7e..074028e 100644
--- a/gdb/testsuite/gdb.debuginfod/crc_mismatch.exp
+++ b/gdb/testsuite/gdb.debuginfod/crc_mismatch.exp
@@ -58,12 +58,39 @@ if {[build_executable crc_mismatch.exp crc_mismatch-2 crc_mismatch-2.c debug] !=
     # to trigger the "CRC mismatch" warning.
     remote_exec build "mv ${debugfile} [standard_output_file crc_mismatch-2.debug]"
 
-    gdb_exit
-    gdb_start
+    clean_restart
 
     set escapedobjdirsubdir [string_to_regexp [standard_output_file {}]]
+    gdb_test "file [standard_output_file crc_mismatch-2]" \
+	[multi_line \
+	     "Reading symbols from ${escapedobjdirsubdir}/crc_mismatch-2\\.\\.\\." \
+	     "warning: the debug information found in \"${escapedobjdirsubdir}/crc_mismatch-2\\.debug\" does not match \"${escapedobjdirsubdir}/crc_mismatch-2\" \\(CRC mismatch\\)\\." \
+	     "\\(No debugging symbols found in .*\\)"] \
+	"CRC mismatch is reported"
+
+    # Do the same thing again, but this time check that the styling is
+    # correct.
+    with_test_prefix "check styling" {
+	save_vars { env(TERM) } {
+	    # We need an ANSI-capable terminal to get styled output.
+	    setenv TERM ansi
+
+	    clean_restart
+
+	    set debug_file_re [style "${escapedobjdirsubdir}/crc_mismatch-2\\.debug" file]
+	    set exe_file_re [style "${escapedobjdirsubdir}/crc_mismatch-2" file]
+
+	    gdb_test "file [standard_output_file crc_mismatch-2]" \
+		[multi_line \
+		     "Reading symbols from ${exe_file_re}\\.\\.\\." \
+		     "warning: the debug information found in \"${debug_file_re}\" does not match \"${exe_file_re}\" \\(CRC mismatch\\)\\." \
+		     "\\(No debugging symbols found in \[^\r\n\]+\\)"] \
+		"CRC mismatch is reported"
+	}
+    }
 
-    gdb_test "file [standard_output_file crc_mismatch-2]" "warning: the debug information found in \"${escapedobjdirsubdir}/crc_mismatch-2\\.debug\" does not match \"${escapedobjdirsubdir}/crc_mismatch-2\" \\(CRC mismatch\\)\\..*\\(No debugging symbols found in .*\\).*" "CRC mismatch is reported"
+    # Restart GDB with styling disabled.
+    clean_restart
 }
 
 # Create CACHE and DB directories ready for debuginfod to use.
diff --git a/gdb/ui-file.h b/gdb/ui-file.h
index de24620..31f87ff 100644
--- a/gdb/ui-file.h
+++ b/gdb/ui-file.h
@@ -30,6 +30,8 @@ public:
   ui_file ();
   virtual ~ui_file () = 0;
 
+  ui_file (ui_file &&other) = default;
+
   /* Public non-virtual API.  */
 
   void printf (const char *, ...) ATTRIBUTE_PRINTF (2, 3);
@@ -177,6 +179,8 @@ public:
   explicit string_file (bool term_out) : m_term_out (term_out) {};
   ~string_file () override;
 
+  string_file (string_file &&other) = default;
+
   /* Override ui_file methods.  */
 
   void write (const char *buf, long length_buf) override;
diff --git a/gdb/utils.h b/gdb/utils.h
index ad0a867..c5364fa 100644
--- a/gdb/utils.h
+++ b/gdb/utils.h
@@ -367,4 +367,56 @@ assign_return_if_changed (T &lval, const T &val)
   return true;
 }
 
+/* In some cases GDB needs to try several different solutions to a problem,
+   if any of the solutions work then as far as the user is concerned the
+   problem is solved, and GDB should continue without warnings.  However,
+   if none of the solutions work then GDB should emit any warnings that
+   occurred while trying each possible solution.
+
+   One example of this is locating separate debug info.  There are several
+   different approaches for this; following the .gnu_debuglink, a build-id
+   based lookup, or using debuginfod.  If any works, and debug info is
+   located, then the user doesn't want to see warnings from the earlier
+   approaches that were tried and failed.
+
+   However, GDB should emit all the warnings using separate calls to
+   warning -- this ensures that each warning is formatted on its own line,
+   and that any styling is emitted correctly.
+
+   This class helps with deferring warnings.  Warnings can be added to an
+   instance of this class with the 'warn' function, and all warnings can be
+   emitted with a single call to 'emit'.  */
+
+struct deferred_warnings
+{
+  /* Add a warning to the list of deferred warnings.  */
+  void warn (const char *format, ...) ATTRIBUTE_PRINTF(2,3)
+  {
+    /* Generate the warning text into a string_file.  We allow the text to
+       be styled only if gdb_stderr allows styling -- warnings are sent to
+       gdb_stderr.  */
+    string_file msg (gdb_stderr->can_emit_style_escape ());
+
+    va_list args;
+    va_start (args, format);
+    msg.vprintf (format, args);
+    va_end (args);
+
+    /* Move the text into the list of deferred warnings.  */
+    m_warnings.emplace_back (std::move (msg));
+  }
+
+  /* Emit all warnings.  */
+  void emit () const
+  {
+    for (const auto &w : m_warnings)
+      warning ("%s", w.c_str ());
+  }
+
+private:
+
+  /* The list of all deferred warnings.  */
+  std::vector<string_file> m_warnings;
+};
+
 #endif /* UTILS_H */