Make 'mmap_realloc' on MS-Windows more reliable

* src/w32heap.c (mmap_alloc): If reserving memory succeeds, but
committing fails, return NULL.  Don't call GetLastError twice for
the same API error.
(mmap_realloc): Zero out MEMORY_BASIC_INFORMATION structures
before calling VirtualQuery, to avoid using garbled values if the
call fails.  If committing more pages from the same block fails,
fall back on mmap_alloc + CopyMemory.  Enhance debugging printouts
if the call to VirtualAlloc to commit more pages fails.
(Bug#22526)

1 files changed, 29 insertions, 22 deletions

diff --git a/src/w32heap.c b/src/w32heap.c
index 00da86a9598..69706a3a57d 100644
--- a/src/w32heap.c
+++ b/src/w32heap.c
@@ -652,15 +652,19 @@ mmap_alloc (void **var, size_t nbytes)
     {
       /* Now, commit pages for NBYTES.  */
       *var = VirtualAlloc (p, nbytes, MEM_COMMIT, PAGE_READWRITE);
+      if (*var == NULL)
+        p = *var;
     }
 
   if (!p)
     {
-      if (GetLastError () == ERROR_NOT_ENOUGH_MEMORY)
+      DWORD e = GetLastError ();
+
+      if (e == ERROR_NOT_ENOUGH_MEMORY)
         errno = ENOMEM;
       else
         {
-          DebPrint (("mmap_alloc: error %ld\n", GetLastError ()));
+          DebPrint (("mmap_alloc: error %ld\n", e));
           errno = EINVAL;
         }
     }
@@ -683,6 +687,7 @@ void *
 mmap_realloc (void **var, size_t nbytes)
 {
   MEMORY_BASIC_INFORMATION memInfo, m2;
+  void *old_ptr;
 
   if (*var == NULL)
     return mmap_alloc (var, nbytes);
@@ -694,12 +699,14 @@ mmap_realloc (void **var, size_t nbytes)
       return mmap_alloc (var, nbytes);
     }
 
+  memset (&memInfo, 0, sizeof (memInfo));
   if (VirtualQuery (*var, &memInfo, sizeof (memInfo)) == 0)
     DebPrint (("mmap_realloc: VirtualQuery error = %ld\n", GetLastError ()));
 
   /* We need to enlarge the block.  */
   if (memInfo.RegionSize < nbytes)
     {
+      memset (&m2, 0, sizeof (m2));
       if (VirtualQuery (*var + memInfo.RegionSize, &m2, sizeof(m2)) == 0)
         DebPrint (("mmap_realloc: VirtualQuery error = %ld\n",
                    GetLastError ()));
@@ -715,31 +722,31 @@ mmap_realloc (void **var, size_t nbytes)
                             MEM_COMMIT, PAGE_READWRITE);
           if (!p /* && GetLastError() != ERROR_NOT_ENOUGH_MEMORY */)
             {
-              DebPrint (("realloc enlarge: VirtualAlloc error %ld\n",
+              DebPrint (("realloc enlarge: VirtualAlloc (%p + %I64x, %I64x) error %ld\n",
+                         *var, (uint64_t)memInfo.RegionSize,
+                         (uint64_t)(nbytes - memInfo.RegionSize),
                          GetLastError ()));
-              errno = ENOMEM;
+              DebPrint (("next region: %p %p %I64x %x\n", m2.BaseAddress,
+                         m2.AllocationBase, m2.RegionSize, m2.AllocationProtect));
             }
+          else
+            return *var;
+        }
+      /* Else we must actually enlarge the block by allocating a new
+         one and copying previous contents from the old to the new one.  */
+      old_ptr = *var;
+
+      if (mmap_alloc (var, nbytes))
+        {
+          CopyMemory (*var, old_ptr, memInfo.RegionSize);
+          mmap_free (&old_ptr);
           return *var;
         }
       else
         {
-          /* Else we must actually enlarge the block by allocating a
-             new one and copying previous contents from the old to the
-             new one.  */
-          void *old_ptr = *var;
-
-          if (mmap_alloc (var, nbytes))
-            {
-              CopyMemory (*var, old_ptr, memInfo.RegionSize);
-              mmap_free (&old_ptr);
-              return *var;
-            }
-          else
-            {
-              /* We failed to enlarge the buffer.  */
-              *var = old_ptr;
-              return NULL;
-            }
+          /* We failed to reallocate the buffer.  */
+          *var = old_ptr;
+          return NULL;
         }
     }
 
@@ -751,7 +758,7 @@ mmap_realloc (void **var, size_t nbytes)
         {
           /* Let's give some memory back to the system and release
              some pages.  */
-          void *old_ptr = *var;
+          old_ptr = *var;
 
           if (mmap_alloc (var, nbytes))
             {