[PATCH] Make caching of memory mappings in sanitizer_procmaps optional

[Sergey Matveev]

    - removed the default constructor and addressed other comments by glider

Hi kcc, glider, samsonov,

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

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D569?vs=1369&id=1389#toc

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

Index: lib/sanitizer_common/sanitizer_linux.cc
===================================================================
--- lib/sanitizer_common/sanitizer_linux.cc
+++ lib/sanitizer_common/sanitizer_linux.cc
@@ -200,7 +200,7 @@
     CHECK_EQ(getrlimit(RLIMIT_STACK, &rl), 0);
 
     // Find the mapping that contains a stack variable.
-    MemoryMappingLayout proc_maps;
+    MemoryMappingLayout proc_maps(true);
     uptr start, end, offset;
     uptr prev_end = 0;
     while (proc_maps.Next(&start, &end, &offset, 0, 0, /* protection */0)) {
@@ -341,18 +341,23 @@
 ProcSelfMapsBuff MemoryMappingLayout::cached_proc_self_maps_;
 StaticSpinMutex MemoryMappingLayout::cache_lock_;  // Linker initialized.
 
-MemoryMappingLayout::MemoryMappingLayout() {
+MemoryMappingLayout::MemoryMappingLayout(bool cache_enabled) {
   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) {
-    LoadFromCache();
-    CHECK_GT(proc_self_maps_.len, 0);
+  if (cache_enabled) {
+    if (proc_self_maps_.mmaped_size == 0) {
+      CHECK(cache_enabled);
+      LoadFromCache();
+      CHECK_GT(proc_self_maps_.len, 0);
+    }
+  } else {
+    CHECK(proc_self_maps_.mmaped_size > 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 (cache_enabled)
+    CacheMemoryMappings();
 }
 
 MemoryMappingLayout::~MemoryMappingLayout() {
Index: lib/sanitizer_common/sanitizer_mac.cc
===================================================================
--- lib/sanitizer_common/sanitizer_mac.cc
+++ lib/sanitizer_common/sanitizer_mac.cc
@@ -165,7 +165,7 @@
 
 // ----------------- sanitizer_procmaps.h
 
-MemoryMappingLayout::MemoryMappingLayout() {
+MemoryMappingLayout::MemoryMappingLayout(bool cache_enabled) {
   Reset();
 }
 
Index: lib/sanitizer_common/sanitizer_posix.cc
===================================================================
--- lib/sanitizer_common/sanitizer_posix.cc
+++ lib/sanitizer_common/sanitizer_posix.cc
@@ -151,19 +151,19 @@
 // several worker threads on Mac, which aren't expected to map big chunks of
 // memory).
 bool MemoryRangeIsAvailable(uptr range_start, uptr range_end) {
-  MemoryMappingLayout procmaps;
+  MemoryMappingLayout proc_maps(true);
   uptr start, end;
-  while (procmaps.Next(&start, &end,
-                       /*offset*/0, /*filename*/0, /*filename_size*/0,
-                       /*protection*/0)) {
+  while (proc_maps.Next(&start, &end,
+                        /*offset*/0, /*filename*/0, /*filename_size*/0,
+                        /*protection*/0)) {
     if (!IntervalsAreSeparate(start, end, range_start, range_end))
       return false;
   }
   return true;
 }
 
 void DumpProcessMap() {
-  MemoryMappingLayout proc_maps;
+  MemoryMappingLayout proc_maps(true);
   uptr start, end;
   const sptr kBufSize = 4095;
   char *filename = (char*)MmapOrDie(kBufSize, __FUNCTION__);
Index: lib/sanitizer_common/sanitizer_procmaps.h
===================================================================
--- lib/sanitizer_common/sanitizer_procmaps.h
+++ lib/sanitizer_common/sanitizer_procmaps.h
@@ -41,7 +41,7 @@
 
 class MemoryMappingLayout {
  public:
-  MemoryMappingLayout();
+  explicit MemoryMappingLayout(bool cache_enabled);
   bool Next(uptr *start, uptr *end, uptr *offset,
             char filename[], uptr filename_size, uptr *protection);
   void Reset();
Index: lib/sanitizer_common/sanitizer_stacktrace.cc
===================================================================
--- lib/sanitizer_common/sanitizer_stacktrace.cc
+++ lib/sanitizer_common/sanitizer_stacktrace.cc
@@ -64,7 +64,7 @@
 void StackTrace::PrintStack(const uptr *addr, uptr size,
                             bool symbolize, const char *strip_file_prefix,
                             SymbolizeCallback symbolize_callback ) {
-  MemoryMappingLayout proc_maps;
+  MemoryMappingLayout proc_maps(true);
   InternalScopedBuffer<char> buff(GetPageSizeCached() * 2);
   InternalScopedBuffer<AddressInfo> addr_frames(64);
   uptr frame_num = 0;
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