[PATCH] Make caching of memory mappings in sanitizer_procmaps optional

[Sergey Matveev]

    - addressed comments by glider

Hi kcc, glider, samsonov,

http://llvm-reviews.chandlerc.com/D569

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D569?vs=1364&id=1369#toc

Files:
  lib/sanitizer_common/sanitizer_linux.cc
  lib/sanitizer_common/sanitizer_mac.cc
  lib/sanitizer_common/sanitizer_procmaps.h

Index: lib/sanitizer_common/sanitizer_linux.cc
===================================================================
--- lib/sanitizer_common/sanitizer_linux.cc
+++ lib/sanitizer_common/sanitizer_linux.cc
@@ -328,17 +328,27 @@
 StaticSpinMutex MemoryMappingLayout::cache_lock_;  // Linker initialized.
 
 MemoryMappingLayout::MemoryMappingLayout() {
+  Init(/*use_cache*/ true);
+}
+
+MemoryMappingLayout::MemoryMappingLayout(bool use_cache) {
+  Init(use_cache);
+}
+
+void MemoryMappingLayout::Init(bool use_cache) {
   proc_self_maps_.len =
       ReadFileToBuffer("/proc/self/maps", &proc_self_maps_.data,
                        &proc_self_maps_.mmaped_size, 1 << 26);
   if (proc_self_maps_.mmaped_size == 0) {
+    CHECK(use_cache);
     LoadFromCache();
     CHECK_GT(proc_self_maps_.len, 0);
   }
   // internal_write(2, proc_self_maps_.data, proc_self_maps_.len);
   Reset();
   // FIXME: in the future we may want to cache the mappings on demand only.
-  CacheMemoryMappings();
+  if (use_cache)
+    CacheMemoryMappings();
 }
 
 MemoryMappingLayout::~MemoryMappingLayout() {
Index: lib/sanitizer_common/sanitizer_mac.cc
===================================================================
--- lib/sanitizer_common/sanitizer_mac.cc
+++ lib/sanitizer_common/sanitizer_mac.cc
@@ -166,6 +166,14 @@
 // ----------------- sanitizer_procmaps.h
 
 MemoryMappingLayout::MemoryMappingLayout() {
+  Init(/*use_cache*/true);
+}
+
+MemoryMappingLayout::MemoryMappingLayout(bool use_cache) {
+  Init(use_cache);
+}
+
+void MemoryMappingLayout::Init(bool use_cache) {
   Reset();
 }
 
Index: lib/sanitizer_common/sanitizer_procmaps.h
===================================================================
--- lib/sanitizer_common/sanitizer_procmaps.h
+++ lib/sanitizer_common/sanitizer_procmaps.h
@@ -42,6 +42,7 @@
 class MemoryMappingLayout {
  public:
   MemoryMappingLayout();
+  explicit MemoryMappingLayout(bool use_cache);
   bool Next(uptr *start, uptr *end, uptr *offset,
             char filename[], uptr filename_size, uptr *protection);
   void Reset();
@@ -63,6 +64,7 @@
   static const uptr kProtectionShared = 8;
 
  private:
+  void Init(bool use_cache);
   void LoadFromCache();
   // Default implementation of GetObjectNameAndOffset.
   // Quite slow, because it iterates through the whole process map for each
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