Implement _malloc_usable_size

1 files changed, 32 insertions, 0 deletions

diff --git a/vespamalloc/src/tests/test1/new_test.cpp b/vespamalloc/src/tests/test1/new_test.cpp
index a8392363f6f..9c291b3842e 100644
--- a/vespamalloc/src/tests/test1/new_test.cpp
+++ b/vespamalloc/src/tests/test1/new_test.cpp
@@ -1,6 +1,8 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 #include <vespa/vespalib/testkit/testapp.h>
 #include <vespa/log/log.h>
+#include <malloc.h>
+#include <dlfcn.h>
 
 LOG_SETUP("new_test");
 
@@ -105,5 +107,35 @@ TEST("verify new with alignment = 64 with single element") {
     LOG(info, "&s=%p", s.get());
 }
 
+void verify_vespamalloc_usable_size() {
+    struct AllocInfo { size_t requested; size_t usable;};
+    AllocInfo allocInfo[] = {{0x7, 0x20}, {0x27, 0x40}, {0x47, 0x80}, {0x87, 0x100}, {0x107, 0x200}, {0x207, 0x400},
+                            {0x407, 0x800}, {0x807, 0x1000}, {0x1007, 0x2000}, {0x2007, 0x4000}, {0x4007, 0x8000},
+                            {0x8007, 0x10000}, {0x10007, 0x20000}, {0x20007, 0x40000}, {0x40007, 0x80000}, {0x80007, 0x100000},
+                            {0x100007, 0x200000}, {0x200007, 0x400000}, {0x400007, 0x600000}};
+    for (const AllocInfo & info : allocInfo) {
+        std::unique_ptr<char[]> buf = std::make_unique<char[]>(info.requested);
+        size_t usable_size = malloc_usable_size(buf.get());
+        EXPECT_EQUAL(info.usable, usable_size);
+    }
+}
+
+TEST("verify malloc_usable_size is sane") {
+    constexpr size_t SZ = 33;
+    std::unique_ptr<char[]> buf = std::make_unique<char[]>(SZ);
+    size_t usable_size = malloc_usable_size(buf.get());
+    if (dlsym(RTLD_NEXT, "is_vespamallocd") != nullptr) {
+        // Debug variants will never have more memory available as there is pre/postamble for error detection.
+        EXPECT_EQUAL(SZ, usable_size);
+    } else if (dlsym(RTLD_NEXT, "is_vespamalloc") != nullptr) {
+        // Normal production vespamalloc will round up
+        EXPECT_EQUAL(64u, usable_size);
+        verify_vespamalloc_usable_size();
+    } else {
+        // Non vespamalloc implementations we can not say anything about
+        EXPECT_GREATER_EQUAL(usable_size, SZ);
+    }
+}
+
 
 TEST_MAIN() { TEST_RUN_ALL(); }