remove string_view STL dependency (#703)

* remove string_view STL dependency

* fix

* inline string literal handling directly

* simplify dispatch

src/snmalloc/ds_core/concept.h

@@ -71,6 +71,7 @@ namespace snmalloc
    */
   template<typename, typename = void>
   constexpr bool is_type_complete_v = false;
+
   template<typename T>
   constexpr bool is_type_complete_v<T, std::void_t<decltype(sizeof(T))>> = true;
 

src/snmalloc/ds_core/helpers.h

@@ -4,7 +4,7 @@
 
 #include <array>
 #include <atomic>
-#include <string_view>
+#include <cstddef>
 #include <tuple>
 #include <type_traits>
 
@@ -192,11 +192,12 @@ namespace snmalloc
     /**
      * Append a string to the buffer.
      */
-    void append(std::string_view sv)
+    template<size_t N>
+    void append(const char (&s)[N])
     {
-      for (auto c : sv)
+      for (size_t i = 0; i < N - 1; i++)
       {
-        append_char(c);
+        append_char(s[i]);
       }
     }
 
@@ -224,15 +225,45 @@ namespace snmalloc
     }
 #endif
 
+    /**
+     * Append a nullptr
+     */
+    void append(std::nullptr_t)
+    {
+      append("(nullptr)");
+    }
+
     /**
      * Append a raw pointer to the buffer as a hex string.
      */
     void append(void* ptr)
     {
+      if (ptr == nullptr)
+      {
+        append(nullptr);
+        return;
+      }
       append(static_cast<unsigned long long>(reinterpret_cast<uintptr_t>(ptr)));
       // TODO: CHERI bits.
     }
 
+    /**
+     * Append a literal pointer.
+     */
+    void append(const char* ptr)
+    {
+      if (ptr == nullptr)
+      {
+        append(nullptr);
+        return;
+      }
+
+      while (char data = *ptr++)
+      {
+        append_char(data);
+      }
+    }
+
     /**
      * Append a signed integer to the buffer, as a decimal string.
      */

src/snmalloc/pal/pal.h

@@ -159,9 +159,7 @@ namespace snmalloc
    * The following are supported as arguments:
    *
    *  - Characters (`char`), printed verbatim.
-   *  - Strings (anything convertible to `std::string_view`), typically string
-   *    literals because nothing on this path should be performing heap
-   *    allocations.  Printed verbatim.
+   *  - Strings Literals (`const char*` or `const char[]`), printed verbatim.
    *  - Raw pointers (void*), printed as hex strings.
    *  - Integers (convertible to `size_t`), printed as hex strings.
    *

src/test/func/malloc/malloc.cc

@@ -232,7 +232,8 @@ int main(int argc, char** argv)
     1234567};
   if (
     strcmp(
-      "testing pointer 0x42 size_t 0x2a message, hello world, null is 0x0, "
+      "testing pointer 0x42 size_t 0x2a message, hello world, null is "
+      "(nullptr), "
       "-123456 is -123456, 1234567 is 1234567",
       b.get_message()) != 0)
   {