From 78906c655566249da0f14c4e23653ea52bd1f571 Mon Sep 17 00:00:00 2001
From: Lang Hames <lhames@gmail.com>
Date: Tue, 7 Apr 2015 06:27:56 +0000
Subject: [PATCH] [RuntimeDyld] Always allocate at least 1 byte for object
 sections in the JIT to ensure that section addresses are distinct.

mapSectionAddress will fail if two sections are allocated the same address,
which can happen if any section has zero size (since malloc(0) is implementation
defined). Unfortunately I've been unable to repro this with a simple test case.

Fixes <rdar://problem/20314015>.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234299 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../RuntimeDyld/RuntimeDyld.cpp               | 29 ++++++++++---------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index a12f0e00588..07aa20b3bc9 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -361,19 +361,20 @@ void RuntimeDyldImpl::computeTotalAllocSize(const ObjectFile &Obj,
       if (Name == ".eh_frame")
         SectionSize += 4;
 
-      if (SectionSize > 0) {
-        // save the total size of the section
-        if (IsCode) {
-          CodeSectionSizes.push_back(SectionSize);
-        } else if (IsReadOnly) {
-          ROSectionSizes.push_back(SectionSize);
-        } else {
-          RWSectionSizes.push_back(SectionSize);
-        }
-        // update the max alignment
-        if (Alignment > MaxAlignment) {
-          MaxAlignment = Alignment;
-        }
+      if (!SectionSize)
+        SectionSize = 1;
+
+      if (IsCode) {
+        CodeSectionSizes.push_back(SectionSize);
+      } else if (IsReadOnly) {
+        ROSectionSizes.push_back(SectionSize);
+      } else {
+        RWSectionSizes.push_back(SectionSize);
+      }
+
+      // update the max alignment
+      if (Alignment > MaxAlignment) {
+        MaxAlignment = Alignment;
       }
     }
   }
@@ -578,6 +579,8 @@ unsigned RuntimeDyldImpl::emitSection(const ObjectFile &Obj,
   if (IsRequired) {
     Check(Section.getContents(data));
     Allocate = DataSize + PaddingSize + StubBufSize;
+    if (!Allocate)
+      Allocate = 1;
     Addr = IsCode ? MemMgr.allocateCodeSection(Allocate, Alignment, SectionID,
                                                Name)
                   : MemMgr.allocateDataSection(Allocate, Alignment, SectionID,