[Bug pch/14940] PCH largefile test fails on various platforms

["xricht17 at stud dot fit.vutbr.cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=14940

--- Comment #50 from Martin Richter <xricht17 at stud dot fit.vutbr.cz> ---
The following patch fixes segfault when gt_pch_use_address fails (returns -1).
fatal_error now correctly shows an error message and terminates the program.
I have basicly only reordered reads, and placed them after the file mapping
itself. Global pointers are changed only after gt_pch_use_address succeeds, so
in case of failure they still contain valid addresses.

This patch is meant for the master branch. However, it should not be hard to
modify it for others.


diff --git a/gcc/ggc-common.c b/gcc/ggc-common.c
index 5096837..f741f2c 100644
--- a/gcc/ggc-common.c
+++ b/gcc/ggc-common.c
@@ -599,7 +599,9 @@ gt_pch_restore (FILE *f)
   size_t i;
   struct mmap_info mmi;
   int result;
-
+  long pch_tabs_off;
+  long pch_data_off;
+  
   /* Delete any deletable objects.  This makes ggc_pch_read much
      faster, as it can be sure that no GCable objects remain other
      than the ones just read in.  */
@@ -607,20 +609,24 @@ gt_pch_restore (FILE *f)
     for (rti = *rt; rti->base != NULL; rti++)
       memset (rti->base, 0, rti->stride);

-  /* Read in all the scalar variables.  */
+  /* We need to read tables after mapping, or fatal_error will
+     segfault when gt_pch_use_address returns -1. Skip them for now. */
+  pch_tabs_off = ftell(f);
+     
+  /* Skip all the scalar variables. */
   for (rt = gt_pch_scalar_rtab; *rt; rt++)
     for (rti = *rt; rti->base != NULL; rti++)
-      if (fread (rti->base, rti->stride, 1, f) != 1)
-       fatal_error (input_location, "can%'t read PCH file: %m");
+      if (fseek (f, rti->stride, SEEK_CUR) != 0)
+        fatal_error (input_location, "can%'t read PCH file: %m");

-  /* Read in all the global pointers, in 6 easy loops.  */
+  /* Skip all the global pointers. */
   for (rt = gt_ggc_rtab; *rt; rt++)
     for (rti = *rt; rti->base != NULL; rti++)
       for (i = 0; i < rti->nelt; i++)
-       if (fread ((char *)rti->base + rti->stride * i,
-                  sizeof (void *), 1, f) != 1)
-         fatal_error (input_location, "can%'t read PCH file: %m");
-
+        if (fseek (f, sizeof (void *), SEEK_CUR) != 0)
+          fatal_error (input_location, "can%'t read PCH file: %m");
+          
+  /* mmi still has to be read now. */          
   if (fread (&mmi, sizeof (mmi), 1, f) != 1)
     fatal_error (input_location, "can%'t read PCH file: %m");

@@ -631,12 +637,35 @@ gt_pch_restore (FILE *f)
   if (result == 0)
     {
       if (fseek (f, mmi.offset, SEEK_SET) != 0
-         || fread (mmi.preferred_base, mmi.size, 1, f) != 1)
-       fatal_error (input_location, "can%'t read PCH file: %m");
+          || fread (mmi.preferred_base, mmi.size, 1, f) != 1)
+        fatal_error (input_location, "can%'t read PCH file: %m");
     }
   else if (fseek (f, mmi.offset + mmi.size, SEEK_SET) != 0)
     fatal_error (input_location, "can%'t read PCH file: %m");
+    
+  /* File mapping done, read tables now. */
+  pch_data_off = ftell(f);
+  
+  if (fseek (f, pch_tabs_off, SEEK_SET) != 0)
+    fatal_error (input_location, "can%'t read PCH file: %m");

+  /* Read in all the scalar variables.  */
+  for (rt = gt_pch_scalar_rtab; *rt; rt++)
+    for (rti = *rt; rti->base != NULL; rti++)
+      if (fread (rti->base, rti->stride, 1, f) != 1)
+        fatal_error (input_location, "can%'t read PCH file: %m");
+
+  /* Read in all the global pointers, in 6 easy loops.  */
+  for (rt = gt_ggc_rtab; *rt; rt++)
+    for (rti = *rt; rti->base != NULL; rti++)
+      for (i = 0; i < rti->nelt; i++)
+        if (fread ((char *)rti->base + rti->stride * i,
+            sizeof (void *), 1, f) != 1)
+          fatal_error (input_location, "can%'t read PCH file: %m");
+
+  if (fseek (f, pch_data_off, SEEK_SET) != 0)
+    fatal_error (input_location, "can%'t read PCH file: %m");
+            
   ggc_pch_read (f, mmi.preferred_base);

   gt_pch_restore_stringpool ();