[compiler-rt] [asan] Refactor DescribeAddressIfStack to allow reuse for debugging API

[kubamracek]

Summary

Refactoring the DescribeAddressIfStack function in asan_report.cc to be able to reuse it for http://reviews.llvm.org/D4527. The plan is to use the newly extracted functions in this manner:

const char *frame_descr = t->GetFrameNameByAddr(addr, &offset, &frame_pc);
InternalMmapVector <StackVarDescr> vars(16);
ParseFrameDescription(frame_descr, vars);
for (uptr i = 0; i < vars.size(); i++) {
... do stuff ...
}

[samsonov]

lib/asan/asan_report.h

36

Consider the following interface instead:

bool ParseFrameDescription(const char *frame_descr, InternalMmapVector<StackVarDescr> *vars);

Note that I passed "vars" by pointer here - we generally don't use non-const references as output parameters in sanitizer runtimes.

[kubamracek]

Updated the interface to use InternalMmapVector instead.

[samsonov]

Please upload the patches with more context.

lib/asan/asan_report.cc

351

While you're here, please initialize the variables in declaration

uptr beg = (uptr)internal_simple_stroll(p, &p, 10);
...

411

You should probably return from the function here.

[samsonov]

LGTM modulo nit below.

lib/asan/asan_report.cc

358

Again, please make sure this is supported by MSVC.

[kubamracek]

Changed the struct initializer to an explicit variable, which is present in other parts of ASan code, so it should be MSVC-safe.

[kubamracek]

Landed in r213215.

lib/asan/asan_report.h

 
 namespace __asan {
 
+struct StackVarDescr {
+  uptr beg;
+  uptr size;
+  const char *name_pos;
+  uptr name_len;
+};
+
 // The following functions prints address description depending
 // on the memory type (shadow/heap/stack/global).
 void DescribeHeapAddress(uptr addr, uptr access_size);

 bool DescribeAddressRelativeToGlobal(uptr addr, uptr access_size,
                                      const __asan_global &g);
 bool DescribeAddressIfShadow(uptr addr);
+uptr NumberOfVarsInFrame(const char *frame_descr);
+bool GetFrameVars(const char *frame_descr,
+                  InternalScopedBuffer<StackVarDescr> &vars, uptr n_objects);
 bool DescribeAddressIfStack(uptr addr, uptr access_size);
 // Determines memory type on its own.
 void DescribeAddress(uptr addr, uptr access_size);

lib/asan/asan_report.cc

   Printf("%s", str.data());
 }
 
-struct StackVarDescr {
-  uptr beg;
-  uptr size;
-  const char *name_pos;
-  uptr name_len;
-};
+uptr NumberOfVarsInFrame(const char *frame_descr) {
+  char *p;
+  uptr n_objects = (uptr)internal_simple_strtoll(frame_descr, &p, 10);
+  CHECK_GT(n_objects, 0);
+  return n_objects;
+}
 
+bool GetFrameVars(const char *frame_descr,
+                  InternalScopedBuffer<StackVarDescr> &vars, uptr n_objects) {
+  char *p;
+  uptr n = (uptr)internal_simple_strtoll(frame_descr, &p, 10);
+  CHECK_EQ(n, n_objects);
+
+  for (uptr i = 0; i < n_objects; i++) {
+    uptr beg, size;
+    uptr len;
+    beg  = (uptr)internal_simple_strtoll(p, &p, 10);
+    size = (uptr)internal_simple_strtoll(p, &p, 10);
+    len  = (uptr)internal_simple_strtoll(p, &p, 10);
+    if (beg == 0 || size == 0 || *p != ' ') {
+      return false;
+    }
+    p++;
+    vars[i].beg = beg;
+    vars[i].size = size;
+    vars[i].name_pos = p;
+    vars[i].name_len = len;
+    p += len;
+  }
+
+  return true;
+}
+
 bool DescribeAddressIfStack(uptr addr, uptr access_size) {
   AsanThread *t = FindThreadByStackAddress(addr);
   if (!t) return false;

   Printf("%s", d.EndLocation());
   alloca_stack.Print();
   // Report the number of stack objects.
-  char *p;
-  uptr n_objects = (uptr)internal_simple_strtoll(frame_descr, &p, 10);
-  CHECK_GT(n_objects, 0);
+  uptr n_objects = NumberOfVarsInFrame(frame_descr);
   Printf("  This frame has %zu object(s):\n", n_objects);
+  InternalScopedBuffer<StackVarDescr> vars(n_objects);
+  if (!GetFrameVars(frame_descr, vars, n_objects)) {
+    Printf("AddressSanitizer can't parse the stack frame "
+           "descriptor: |%s|\n", frame_descr);
+  }
 
   // Report all objects in this frame.
-  InternalScopedBuffer<StackVarDescr> vars(n_objects);
   for (uptr i = 0; i < n_objects; i++) {
-    uptr beg, size;
-    uptr len;
-    beg  = (uptr)internal_simple_strtoll(p, &p, 10);
-    size = (uptr)internal_simple_strtoll(p, &p, 10);
-    len  = (uptr)internal_simple_strtoll(p, &p, 10);
-    if (beg == 0 || size == 0 || *p != ' ') {
-      Printf("AddressSanitizer can't parse the stack frame "
-                 "descriptor: |%s|\n", frame_descr);
-      break;
-    }
-    p++;
-    vars[i].beg = beg;
-    vars[i].size = size;
-    vars[i].name_pos = p;
-    vars[i].name_len = len;
-    p += len;
-  }
-  for (uptr i = 0; i < n_objects; i++) {
     buf[0] = 0;
     internal_strncat(buf, vars[i].name_pos,
                      static_cast<uptr>(Min(kBufSize, vars[i].name_len)));