[c-family] Backport fix for PCH / 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.

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

This leads to the pch bug 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/

2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>

	Backport from mainline
	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.

gcc/c-family/

2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>

	Backport from mainline
	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/

2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>

	Backport from mainline.
	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/

2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>

	Backported from mainline
	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.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-9-branch@275246 138bc75d-0d04-0410-961f-82ee72b054a4

8 files changed, 48 insertions, 10 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f3a53408f85..3ae23dbc01b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>
+
+	Backport from mainline
+	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.
+
 2019-08-30  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	Backport from trunk
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index acdfe79894e..8fa6963f186 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,12 @@
+2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>
+
+	Backport from mainline
+	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.
+
 2019-08-12  Release Manager
 
 	* GCC 9.2.0 released.
diff --git a/gcc/c-family/c-lex.c b/gcc/c-family/c-lex.c
index 0a368a33a58..3c92103a5d4 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 89e5b25d020..b98aa517ff2 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,13 @@
+2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>
+
+	Backport from mainline.
+	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.
+
 2019-08-12  Release Manager
 
 	* GCC 9.2.0 released.
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index f8d1fb3fa78..3b58dc368de 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -19859,6 +19859,8 @@ 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 adc0a839708..da73772c99e 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,13 @@
+2019-08-31  Iain Sandoe  <iain@sandoe.co.uk>
+
+	Backported from mainline
+	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.
+
 2019-08-23  Marek Polacek  <polacek@redhat.com>
 
 	Backported from mainline
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 58b44abd109..09251bf2135 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -40751,7 +40751,10 @@ 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 143986be58f..cd531e5b1e6 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, "can%'t read PCH file: %m");
 
   for (i = 0; i < NUM_ORDERS; i++)
     {