diagnostic: Save/restore diagnostic context history and push/pop state for PCH [PR116847]

The following patch on top of the just posted cleanup patch
saves/restores the m_classification_history and m_push_list
vectors for PCH.  Without that as the testcase shows during parsing
of the templates we don't report ignored diagnostics, but after loading
PCH header when instantiating those templates those warnings can be
emitted.  This doesn't show up on x86_64-linux build because configure
injects there -fcf-protection -mshstk flags during library build (and so
also during PCH header creation), but make check doesn't use those flags
and so the PCH header is ignored.

2024-09-26  Jakub Jelinek  <jakub@redhat.com>

	PR libstdc++/116847
gcc/
	* diagnostic.h (diagnostic_option_classifier): Add pch_save and
	pch_restore method declarations.
	(diagnostic_context): Add pch_save and pch_restore inline method
	definitions.
	* diagnostic.cc (diagnostic_option_classifier::pch_save): New method.
	(diagnostic_option_classifier::pch_restore): Likewise.
gcc/c-family/
	* c-pch.cc: Include diagnostic.h.
	(c_common_write_pch): Call global_dc->pch_save.
	(c_common_read_pch): Call global_dc->pch_restore.
gcc/testsuite/
	* g++.dg/pch/pr116847.C: New test.
	* g++.dg/pch/pr116847.Hs: New test.

5 files changed, 80 insertions, 1 deletions

diff --git a/gcc/c-family/c-pch.cc b/gcc/c-family/c-pch.cc
index 9bcfdc8..f104575 100644
--- a/gcc/c-family/c-pch.cc
+++ b/gcc/c-family/c-pch.cc
@@ -28,6 +28,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "c-pragma.h"
 #include "langhooks.h"
 #include "hosthooks.h"
+#include "diagnostic.h"
 
 /* This is a list of flag variables that must match exactly, and their
    names for the error message.  The possible values for *flag_var must
@@ -178,7 +179,8 @@ c_common_write_pch (void)
   cpp_write_pch_state (parse_in, pch_outfile);
   timevar_pop (TV_PCH_CPP_SAVE);
 
-  if (fseek (pch_outfile, 0, SEEK_SET) != 0
+  if (global_dc->pch_save (pch_outfile) < 0
+      || fseek (pch_outfile, 0, SEEK_SET) != 0
       || fwrite (get_ident (), IDENT_LENGTH, 1, pch_outfile) != 1)
     fatal_error (input_location, "cannot write %s: %m", pch_file);
 
@@ -359,6 +361,10 @@ c_common_read_pch (cpp_reader *pfile, const char *name,
   linemap_line_start (line_table, saved_loc.line, 0);
 
   timevar_pop (TV_PCH_CPP_RESTORE);
+
+  if (global_dc->pch_restore (f) < 0)
+    fatal_error (input_location, "cannot read %s: %m", name);
+
   fclose (f);
 
   if (cpp_result != 0)
diff --git a/gcc/diagnostic.cc b/gcc/diagnostic.cc
index ffe61f7..9462fe6 100644
--- a/gcc/diagnostic.cc
+++ b/gcc/diagnostic.cc
@@ -156,6 +156,46 @@ diagnostic_option_classifier::fini ()
   m_push_list.release ();
 }
 
+/* Save the diagnostic_option_classifier state to F for PCH
+   output.  Returns 0 on success, -1 on error.  */
+
+int
+diagnostic_option_classifier::pch_save (FILE *f)
+{
+  unsigned int lengths[2] = { m_classification_history.length (),
+			      m_push_list.length () };
+  if (fwrite (lengths, sizeof (lengths), 1, f) != 1
+      || fwrite (m_classification_history.address (),
+		 sizeof (diagnostic_classification_change_t),
+		 lengths[0], f) != lengths[0]
+      || fwrite (m_push_list.address (), sizeof (int),
+		 lengths[1], f) != lengths[1])
+    return -1;
+  return 0;
+}
+
+/* Read the diagnostic_option_classifier state from F for PCH
+   read.  Returns 0 on success, -1 on error.  */
+
+int
+diagnostic_option_classifier::pch_restore (FILE *f)
+{
+  unsigned int lengths[2];
+  if (fread (lengths, sizeof (lengths), 1, f) != 1)
+    return -1;
+  gcc_checking_assert (m_classification_history.is_empty ());
+  gcc_checking_assert (m_push_list.is_empty ());
+  m_classification_history.safe_grow (lengths[0]);
+  m_push_list.safe_grow (lengths[1]);
+  if (fread (m_classification_history.address (),
+	     sizeof (diagnostic_classification_change_t),
+	     lengths[0], f) != lengths[0]
+      || fread (m_push_list.address (), sizeof (int),
+		lengths[1], f) != lengths[1])
+    return -1;
+  return 0;
+}
+
 /* Save all diagnostic classifications in a stack.  */
 
 void
diff --git a/gcc/diagnostic.h b/gcc/diagnostic.h
index c3300fc..3087b19 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -256,6 +256,9 @@ public:
   diagnostic_t
   update_effective_level_from_pragmas (diagnostic_info *diagnostic) const;
 
+  int pch_save (FILE *);
+  int pch_restore (FILE *);
+
 private:
   /* Each time a diagnostic's classification is changed with a pragma,
      we record the change and the location of the change in an array of
@@ -551,6 +554,18 @@ public:
 			  const char *, const char *, va_list *,
 			  diagnostic_t) ATTRIBUTE_GCC_DIAG(7,0);
 
+  int
+  pch_save (FILE *f)
+  {
+    return m_option_classifier.pch_save (f);
+  }
+
+  int
+  pch_restore (FILE *f)
+  {
+    return m_option_classifier.pch_restore (f);
+  }
+
 private:
   void error_recursion () ATTRIBUTE_NORETURN;
 
diff --git a/gcc/testsuite/g++.dg/pch/pr116847.C b/gcc/testsuite/g++.dg/pch/pr116847.C
new file mode 100644
index 0000000..e1e4344
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pch/pr116847.C
@@ -0,0 +1,10 @@
+// { dg-do compile { target c++11 } }
+
+#include "pr116847.H"
+
+int a = S<0>::bar ();
+
+int
+main ()
+{
+}
diff --git a/gcc/testsuite/g++.dg/pch/pr116847.Hs b/gcc/testsuite/g++.dg/pch/pr116847.Hs
new file mode 100644
index 0000000..89bbb2d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pch/pr116847.Hs
@@ -0,0 +1,8 @@
+[[deprecated]] int foo () { return 42; }
+template <int N>
+struct S {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+static int bar () { return foo (); }
+#pragma GCC diagnostic pop
+};