alloc: minimal allocator for inspections

1 files changed, 87 insertions, 0 deletions

diff --git a/dbg_alloc.cc b/dbg_alloc.cc
new file mode 100644
index 0000000..c1b7490
--- /dev/null
+++ b/dbg_alloc.cc
@@ -0,0 +1,87 @@
+#if 0
+set -xe
+trap "rm -f a.out" EXIT
+clang++ -std=c++17 dbg_alloc.cc && ./a.out
+g++     -std=c++17 dbg_alloc.cc && ./a.out
+exit 0
+#endif
+
+#include <cassert>
+#include <cstdio>
+#include <cstdlib>
+
+template <typename T>
+class dbg_alloc {
+  inline static std::size_t INST_CNT = 0;
+  std::size_t inst                   = INST_CNT++;
+
+public:
+  using value_type = T;
+
+  dbg_alloc() = default;
+
+  template <typename U>
+  dbg_alloc(const dbg_alloc<U>&) {
+  }
+
+  T* allocate(std::size_t size) noexcept {
+    assert(size > 0);
+    T* ptr = static_cast<T*>(std::calloc(sizeof(T), size));
+    std::fprintf(stderr, "[%2zu] alloc   %8zu (%p)\n", inst, size, ptr);
+    return ptr;
+  }
+
+  void deallocate(T* ptr, std::size_t size) noexcept {
+    std::fprintf(stderr, "[%2zu] dealloc %8zu (%p)\n", inst, size, ptr);
+    std::free(ptr);
+  }
+};
+
+// -- EXAMPLE ------------------------------------------------------------------
+
+#include <map>
+#include <set>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+int main() {
+  {
+    puts("-- std::vector");
+    std::vector<int, dbg_alloc<int>> o;
+    for (int i = 0; i < 5; ++i) {
+      o.push_back(i);
+    }
+  }
+  {
+    puts("-- std::set");
+    std::set<int, std::less<int>, dbg_alloc<int>> o;
+    for (int i = 0; i < 5; ++i) {
+      o.insert(i);
+    }
+  }
+  {
+    puts("-- std::unordered_set");
+    std::unordered_set<int, std::hash<int>, std::equal_to<int>, dbg_alloc<int>>
+        o;
+    for (int i = 0; i < 5; ++i) {
+      o.insert(i);
+    }
+  }
+  {
+    puts("-- std::map");
+    std::map<int, int, std::less<int>, dbg_alloc<std::pair<const int, int>>> o;
+    for (int i = 0; i < 5; ++i) {
+      o[i] = i * 2;
+    }
+  }
+  {
+    puts("-- std::unordered_map");
+    std::unordered_map<int, int, std::hash<int>, std::equal_to<int>,
+                       dbg_alloc<std::pair<const int, int>>>
+        o;
+    for (int i = 0; i < 5; ++i) {
+      o[i] = i * 2;
+    }
+  }
+}