[pushed:,r15-4081] diagnostics: bulletproof opening of SARIF output [PR116978]

diff --git a/gcc/diagnostic-format-sarif.cc b/gcc/diagnostic-format-sarif.cc
index aeba9f9ceef3..f053dec19205 100644
--- a/gcc/diagnostic-format-sarif.cc
+++ b/gcc/diagnostic-format-sarif.cc
@@ -1510,9 +1510,10 @@  sarif_builder::sarif_builder (diagnostic_context &context,
      since otherwise the "no diagnostics" case would quote the main input
      file, and doing so noticeably bloated the output seen in analyzer
      integration testing (build directory went from 20G -> 21G).  */
-  get_or_create_artifact (main_input_filename_,
-			  diagnostic_artifact_role::analysis_target,
-			  false);
+  if (main_input_filename_)
+    get_or_create_artifact (main_input_filename_,
+			    diagnostic_artifact_role::analysis_target,
+			    false);
 }
 
 sarif_builder::~sarif_builder ()
@@ -3239,29 +3240,17 @@  public:
 			    const char *main_input_filename_,
 			    bool formatted,
 			    enum sarif_version version,
-			    const char *base_file_name)
+			    diagnostic_output_file output_file)
   : sarif_output_format (context, line_maps, main_input_filename_,
 			 formatted, version),
-    m_base_file_name (xstrdup (base_file_name))
+    m_output_file (std::move (output_file))
   {
+    gcc_assert (m_output_file.get_open_file ());
+    gcc_assert (m_output_file.get_filename ());
   }
   ~sarif_file_output_format ()
   {
-    char *filename = concat (m_base_file_name, ".sarif", nullptr);
-    free (m_base_file_name);
-    m_base_file_name = nullptr;
-    FILE *outf = fopen (filename, "w");
-    if (!outf)
-      {
-	const char *errstr = xstrerror (errno);
-	fnotice (stderr, "error: unable to open '%s' for writing: %s\n",
-		 filename, errstr);
-	free (filename);
-	return;
-      }
-    m_builder.flush_to_file (outf);
-    fclose (outf);
-    free (filename);
+    m_builder.flush_to_file (m_output_file.get_open_file ());
   }
   bool machine_readable_stderr_p () const final override
   {
@@ -3269,7 +3258,7 @@  public:
   }
 
 private:
-  char *m_base_file_name;
+  diagnostic_output_file m_output_file;
 };
 
 /* Print the start of an embedded link to PP, as per 3.11.6.  */
@@ -3435,13 +3424,35 @@  diagnostic_output_format_init_sarif_stderr (diagnostic_context &context,
 
 void
 diagnostic_output_format_init_sarif_file (diagnostic_context &context,
-					  const line_maps *line_maps,
+					  line_maps *line_maps,
 					  const char *main_input_filename_,
 					  bool formatted,
 					  enum sarif_version version,
 					  const char *base_file_name)
 {
   gcc_assert (line_maps);
+
+  if (!base_file_name)
+    {
+      rich_location richloc (line_maps, UNKNOWN_LOCATION);
+      context.emit_diagnostic (DK_ERROR, richloc, nullptr, 0,
+			       "unable to determine filename for SARIF output");
+      return;
+    }
+
+  label_text filename = label_text::take (concat (base_file_name,
+						  ".sarif",
+						  nullptr));
+  FILE *outf = fopen (filename.get (), "w");
+  if (!outf)
+    {
+      rich_location richloc (line_maps, UNKNOWN_LOCATION);
+      context.emit_diagnostic (DK_ERROR, richloc, nullptr, 0,
+			       "unable to open %qs for SARIF output: %m",
+			       filename.get ());
+      return;
+    }
+  diagnostic_output_file output_file (outf, true, std::move (filename));
   diagnostic_output_format_init_sarif
     (context,
      ::make_unique<sarif_file_output_format> (context,
@@ -3449,7 +3460,7 @@  diagnostic_output_format_init_sarif_file (diagnostic_context &context,
 					      main_input_filename_,
 					      formatted,
 					      version,
-					      base_file_name));
+					      std::move (output_file)));
 }
 
 /* Populate CONTEXT in preparation for SARIF output to STREAM.  */
diff --git a/gcc/diagnostic-format-sarif.h b/gcc/diagnostic-format-sarif.h
index 555ea60a70b4..5f8751aa3505 100644
--- a/gcc/diagnostic-format-sarif.h
+++ b/gcc/diagnostic-format-sarif.h
@@ -23,6 +23,7 @@  along with GCC; see the file COPYING3.  If not see
 
 #include "json.h"
 #include "diagnostic-format.h"
+#include "diagnostic-output-file.h"
 
 class logical_location;
 
@@ -42,7 +43,7 @@  diagnostic_output_format_init_sarif_stderr (diagnostic_context &context,
 					    enum sarif_version version);
 extern void
 diagnostic_output_format_init_sarif_file (diagnostic_context &context,
-					  const line_maps *line_maps,
+					  line_maps *line_maps,
 					  const char *main_input_filename_,
 					  bool formatted,
 					  enum sarif_version version,
diff --git a/gcc/diagnostic-output-file.h b/gcc/diagnostic-output-file.h
new file mode 100644
index 000000000000..f0ae5e1915ec
--- /dev/null
+++ b/gcc/diagnostic-output-file.h
@@ -0,0 +1,75 @@ 
+/* RAII class for managing FILE * for diagnostic formats.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   Contributed by David Malcolm <dmalcolm@redhat.com>.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_DIAGNOSTIC_OUTPUT_FILE_H
+#define GCC_DIAGNOSTIC_OUTPUT_FILE_H
+
+/* RAII class for wrapping a FILE * that could be borrowed or owned,
+   along with the underlying filename.  */
+
+class diagnostic_output_file
+{
+public:
+  diagnostic_output_file (FILE *outf, bool owned, label_text filename)
+  : m_outf (outf),
+    m_owned (owned),
+    m_filename (std::move (filename))
+  {
+    gcc_assert (m_filename.get ());
+    if (m_owned)
+      gcc_assert (m_outf);
+  }
+  ~diagnostic_output_file ()
+  {
+    if (m_owned)
+      {
+	gcc_assert (m_outf);
+	fclose (m_outf);
+      }
+  }
+  diagnostic_output_file (const diagnostic_output_file &other) = delete;
+  diagnostic_output_file (diagnostic_output_file &&other)
+  : m_outf (other.m_outf),
+    m_owned (other.m_owned),
+    m_filename (std::move (other.m_filename))
+  {
+    other.m_outf = nullptr;
+    other.m_owned = false;
+
+    gcc_assert (m_filename.get ());
+    if (m_owned)
+      gcc_assert (m_outf);
+  }
+  diagnostic_output_file &
+  operator= (const diagnostic_output_file &other) = delete;
+  diagnostic_output_file &
+  operator= (diagnostic_output_file &&other) = delete;
+
+  operator bool () const { return m_outf != nullptr; }
+  FILE *get_open_file () const { return m_outf; }
+  const char *get_filename () const { return m_filename.get (); }
+
+private:
+  FILE *m_outf;
+  bool m_owned;
+  label_text m_filename;
+};
+
+#endif /* ! GCC_DIAGNOSTIC_OUTPUT_FILE_H */
diff --git a/gcc/diagnostic.cc b/gcc/diagnostic.cc
index dfedcae58052..c8449d82d185 100644
--- a/gcc/diagnostic.cc
+++ b/gcc/diagnostic.cc
@@ -1178,6 +1178,47 @@  diagnostic_context::warning_enabled_at (location_t loc,
   return diagnostic_enabled (&diagnostic);
 }
 
+/* Emit a diagnostic within a diagnostic group on this context.  */
+
+bool
+diagnostic_context::emit_diagnostic (diagnostic_t kind,
+				     rich_location &richloc,
+				     const diagnostic_metadata *metadata,
+				     diagnostic_option_id option_id,
+				     const char *gmsgid, ...)
+{
+  begin_group ();
+
+  va_list ap;
+  va_start (ap, gmsgid);
+  bool ret = emit_diagnostic_va (kind, richloc, metadata, option_id,
+				 gmsgid, &ap);
+  va_end (ap);
+
+  end_group ();
+
+  return ret;
+}
+
+/* As above, but taking a va_list *.  */
+
+bool
+diagnostic_context::emit_diagnostic_va (diagnostic_t kind,
+					rich_location &richloc,
+					const diagnostic_metadata *metadata,
+					diagnostic_option_id option_id,
+					const char *gmsgid, va_list *ap)
+{
+  begin_group ();
+
+  bool ret = diagnostic_impl (&richloc, metadata, option_id,
+			      gmsgid, ap, kind);
+
+  end_group ();
+
+  return ret;
+}
+
 /* Report a diagnostic message (an error or a warning) as specified by
    this diagnostic_context.
    front-end independent format specifiers are exactly those described
diff --git a/gcc/diagnostic.h b/gcc/diagnostic.h
index fd056bd87225..9c11ee3d1cfe 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -506,6 +506,19 @@  public:
     return m_option_classifier.option_unspecified_p (option_id);
   }
 
+  bool emit_diagnostic (diagnostic_t kind,
+			rich_location &richloc,
+			const diagnostic_metadata *metadata,
+			diagnostic_option_id option_id,
+			const char *gmsgid, ...)
+    ATTRIBUTE_GCC_DIAG(6,7);
+  bool emit_diagnostic_va (diagnostic_t kind,
+			   rich_location &richloc,
+			   const diagnostic_metadata *metadata,
+			   diagnostic_option_id option_id,
+			   const char *gmsgid, va_list *ap)
+    ATTRIBUTE_GCC_DIAG(6,0);
+
   bool report_diagnostic (diagnostic_info *);
 
   void check_max_errors (bool flush);