[scudo][standalone] Make malloc_info return a minimal XML

[cryptoad]

Summary

Initially, our malloc_info was returning ENOTSUP, but Android would
rather have it return successfully and write a barebone XML to the
stream, so we will oblige.

Add an associated test.

[cryptoad]

Changing the version to "scudo-1" as per privately conveyed request.

[cryptoad]

Apparently clang-formatting the tests found an extraneous space in combined_test.cpp as well.

[morehouse]

lib/scudo/standalone/tests/wrappers_c_test.cpp

294 ↗

(On Diff #223106)

Nit: If we move fclose to before the strncmp, we don't need to fflush.

[cryptoad]

Addressing Matt's review comment.

compiler-rt/trunk/lib/scudo/standalone/tests/combined_test.cpp

while (Size > 1U) {
     P = NewP;
   }
   Allocator->deallocate(P, Origin);
 
   // Check that reallocating a chunk to a slightly smaller or larger size
   // returns the same chunk. This requires that all the sizes we iterate on use
   // the same block size, but that should be the case for 2048 with our default
   // class size maps.
-  P  = Allocator->allocate(DataSize, Origin);
+  P = Allocator->allocate(DataSize, Origin);
   memset(P, Marker, DataSize);
   for (scudo::sptr Delta = -32; Delta < 32; Delta += 8) {
     const scudo::uptr NewSize = DataSize + Delta;
     void *NewP = Allocator->reallocate(P, NewSize);
     EXPECT_EQ(NewP, P);
     for (scudo::uptr I = 0; I < scudo::Min(DataSize, NewSize); I++)
       EXPECT_EQ((reinterpret_cast<char *>(NewP))[I], Marker);
   }

compiler-rt/trunk/lib/scudo/standalone/tests/wrappers_c_test.cpp

TEST(ScudoWrappersCTest, MallocIterateBoundary) {
   malloc_disable();
   malloc_iterate(Block - PageSize, PageSize, callback, nullptr);
   malloc_iterate(Block, PageSize, callback, nullptr);
   malloc_enable();
   EXPECT_EQ(Count, 1U);
 
   free(P);
 }
+
+TEST(ScudoWrappersCTest, MallocInfo) {
+  char Buffer[64];
+  FILE *F = fmemopen(Buffer, sizeof(Buffer), "w+");
+  EXPECT_NE(F, nullptr);
+  errno = 0;
+  EXPECT_EQ(malloc_info(0, F), 0);
+  EXPECT_EQ(errno, 0);
+  fclose(F);
+  EXPECT_EQ(strncmp(Buffer, "<malloc version=\"scudo-", 23), 0);
+}

compiler-rt/trunk/lib/scudo/standalone/wrappers_c.inc

if (SCUDO_ALLOCATOR.canReturnNull()) {
       return nullptr;
     }
     scudo::reportInvalidAlignedAllocAlignment(alignment, size);
   }
   return scudo::setErrnoOnNull(
       SCUDO_ALLOCATOR.allocate(size, scudo::Chunk::Origin::Malloc, alignment));
 }
 
-INTERFACE WEAK int SCUDO_PREFIX(malloc_info)(int, FILE *) {
-  errno = ENOTSUP;
-  return -1;
+INTERFACE WEAK int SCUDO_PREFIX(malloc_info)(UNUSED int options, FILE *stream) {
+  fputs("<malloc version=\"scudo-1\">", stream);
+  fputs("</malloc>", stream);
+  return 0;
 }