[PATCH, c-family] Fix a PCH thinko (and thus PR61250).

When we are parsing a source file, the very first token might
be a PRAGMA_GCC_PCH_PREPROCESS.  This indicates that we are going
read in a PCH file (named as the value of the pragma).  If we don't
see this pragma, then we know that it's OK to release any resources
that the host might have set aside for the PCH file.

This fixes a thinko in the current implementation, in that the decision
to release resources was happening unconditionally right after the first
token is extracted but before it's been checked or acted upon.

This leads to the pch bug (seen on Darwin), because we actually do release
resources - which are subsequently (reasonably) assumed to be available
when reading a PCH file.  We then get random crashes or hangs depending
on the interaction between unmmap and malloc.

The bug is present everywhere but doesn't show on (say) Linux, since
the release of PCH resources is a NOP there.

This effects all the c-family front ends, because they all use c_lex_with_flags ()
to implement this.

The solution is to check for the PRAGMA_GCC_PCH_PREPROCESS and only call
c_common_no_more_pch () when that is not the first token.

A secondary effect of the collection is that the name of the PCH file
can be collected during the ggc_pch_read() reset of state.  Therefore
we should issue any diagnostic that might name the file before the
collections are triggered.


gcc/c-family/

2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>

	PR pch/61250
	* c-lex.c (c_lex_with_flags):  Don't call
	c_common_no_more_pch () from here.

gcc/c/

2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>

	PR pch/61250
	* c-parser.c (c_parse_file): Call c_common_no_more_pch ()
	after determining that the first token is not
	PRAGMA_GCC_PCH_PREPROCESS.

gcc/cp/

2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>

	PR pch/61250
	* parser.c (cp_parser_initial_pragma): Call c_common_no_more_pch ()
	after determining that the first token is not
	PRAGMA_GCC_PCH_PREPROCESS.

gcc/

2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>

	PR pch/61250
	* ggc-page.c (ggc_pch_read): Read the ggc_pch_ondisk structure
	and issue any diagnostics needed before collecting the pre-PCH
	state.

From-SVN: r274856

8 files changed, 36 insertions, 10 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 62aebf25ddc..86669dd5cf3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR pch/61250
+	* ggc-page.c (ggc_pch_read): Read the ggc_pch_ondisk structure
+	and issue any diagnostics needed before collecting the pre-PCH
+	state.
+
 2019-08-23  Jakub Jelinek  <jakub@redhat.com>
 
 	PR middle-end/91283
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index b8920f1c18d..2ab1c98b260 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,9 @@
+2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR pch/61250
+	* c-lex.c (c_lex_with_flags):  Don't call
+	c_common_no_more_pch () from here.
+
 2019-08-23  Jakub Jelinek  <jakub@redhat.com>
 
 	PR middle-end/91283
diff --git a/gcc/c-family/c-lex.c b/gcc/c-family/c-lex.c
index 851fd704e5d..e3c602fbb8d 100644
--- a/gcc/c-family/c-lex.c
+++ b/gcc/c-family/c-lex.c
@@ -394,7 +394,6 @@ enum cpp_ttype
 c_lex_with_flags (tree *value, location_t *loc, unsigned char *cpp_flags,
 		  int lex_flags)
 {
-  static bool no_more_pch;
   const cpp_token *tok;
   enum cpp_ttype type;
   unsigned char add_flags = 0;
@@ -628,12 +627,6 @@ c_lex_with_flags (tree *value, location_t *loc, unsigned char *cpp_flags,
   if (cpp_flags)
     *cpp_flags = tok->flags | add_flags;
 
-  if (!no_more_pch)
-    {
-      no_more_pch = true;
-      c_common_no_more_pch ();
-    }
-
   timevar_pop (TV_CPP);
 
   return type;
diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 0b3dc74f50f..b7b45f504a1 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,10 @@
+2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR pch/61250
+	* c-parser.c (c_parse_file): Call c_common_no_more_pch ()
+	after determining that the first token is not
+	PRAGMA_GCC_PCH_PREPROCESS.
+
 2019-08-22  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* c-parser.c (c_parser_declaration_or_fndef): Set DECL_ARGUMENTS of a
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 7397f536032..6070502deb5 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -20263,6 +20263,8 @@ c_parse_file (void)
 
   if (c_parser_peek_token (&tparser)->pragma_kind == PRAGMA_GCC_PCH_PREPROCESS)
     c_parser_pragma_pch_preprocess (&tparser);
+  else
+    c_common_no_more_pch ();
 
   the_parser = ggc_alloc<c_parser> ();
   *the_parser = tparser;
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index d2b96231fd0..f014423ca00 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2019-08-23  Iain Sandoe  <iain@sandoe.co.uk>
+
+	PR pch/61250
+	* parser.c (cp_parser_initial_pragma): Call c_common_no_more_pch ()
+	after determining that the first token is not
+	PRAGMA_GCC_PCH_PREPROCESS.
+
 2019-08-22  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/91304 - prefix attributes ignored in condition.
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index b410a6c030f..504f77a4908 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -41357,7 +41357,10 @@ cp_parser_initial_pragma (cp_token *first_token)
 
   cp_lexer_get_preprocessor_token (NULL, first_token);
   if (cp_parser_pragma_kind (first_token) != PRAGMA_GCC_PCH_PREPROCESS)
-    return;
+    {
+      c_common_no_more_pch ();
+      return;
+    }
 
   cp_lexer_get_preprocessor_token (NULL, first_token);
   if (first_token->type == CPP_STRING)
diff --git a/gcc/ggc-page.c b/gcc/ggc-page.c
index a2736bc1dfa..220f20c5cfe 100644
--- a/gcc/ggc-page.c
+++ b/gcc/ggc-page.c
@@ -2556,6 +2556,9 @@ ggc_pch_read (FILE *f, void *addr)
 
   count_old_page_tables = G.by_depth_in_use;
 
+  if (fread (&d, sizeof (d), 1, f) != 1)
+    fatal_error (input_location, "cannot read PCH file: %m");
+
   /* We've just read in a PCH file.  So, every object that used to be
      allocated is now free.  */
   clear_marks ();
@@ -2584,8 +2587,6 @@ ggc_pch_read (FILE *f, void *addr)
 
   /* Allocate the appropriate page-table entries for the pages read from
      the PCH file.  */
-  if (fread (&d, sizeof (d), 1, f) != 1)
-    fatal_error (input_location, "cannot read PCH file: %m");
 
   for (i = 0; i < NUM_ORDERS; i++)
     {