FixedWidthPointer: Fix ==/!= operators, remove OtherType casts

* FixedWidthPointer:
  - operators ==/!=: Change second operand type from void* to const
    Type*. Also add non-const version to resolve ambiguity warning when
    comparing with non-const pointer.
  - Add Pointer() getter.
  - Remove templatized cast operators. They are nice for casting the
    pointer directly to another pointer type, but result in ambiguity.
* Make preloaded_image::debug_string_table non-const. Avoids clashes of
  the const and non-coast FixedWidthPointer comparison operators. A
  cleaner (but more verbose) solution would be to spezialize
  FixedWidthPointer for const types.

headers/private/kernel/boot/elf.h

@@ -32,7 +32,7 @@ struct preloaded_image {
 	uint8		elf_class;
 	addr_range	dynamic_section;
 
-	FixedWidthPointer<const char> debug_string_table;
+	FixedWidthPointer<char> debug_string_table;
 	uint32		num_debug_symbols;
 	uint32		debug_string_table_size;
 

headers/private/kernel/util/FixedWidthPointer.h

@@ -20,30 +20,29 @@
 template<typename Type>
 class FixedWidthPointer {
 public:
-	operator Type*() const
+	Type * Pointer() const
 	{
 		return (Type*)(addr_t)fValue;
 	}
 
-	template<typename OtherType>
-	operator OtherType*() const
+	operator Type*() const
 	{
-		return static_cast<OtherType*>((Type*)(addr_t)fValue);
+		return Pointer();
 	}
 
 	Type& operator*() const
 	{
-		return *((Type*)(addr_t)fValue);
+		return *Pointer();
 	}
 
 	Type* operator->() const
 	{
-		return (Type*)(addr_t)fValue;
+		return Pointer();
 	}
 
 	Type& operator[](size_t i) const
 	{
-		return ((Type*)(addr_t)fValue)[i];
+		return Pointer()[i];
 	}
 
 	FixedWidthPointer& operator=(const FixedWidthPointer& p)
@@ -85,15 +84,14 @@ private:
 template<>
 class FixedWidthPointer<void> {
 public:
-	operator void*() const
+	void * Pointer() const
 	{
 		return (void*)(addr_t)fValue;
 	}
 
-	template<typename OtherType>
-	operator OtherType*() const
+	operator void*() const
 	{
-		return (OtherType*)(addr_t)fValue;
+		return Pointer();
 	}
 
 	FixedWidthPointer& operator=(const FixedWidthPointer& p)
@@ -122,16 +120,34 @@ private:
 	uint64 fValue;
 } _PACKED;
 
+
 template<typename Type>
 inline bool
-operator==(const FixedWidthPointer<Type>& a, void* b)
+operator==(const FixedWidthPointer<Type>& a, const Type* b)
 {
 	return a.Get() == (addr_t)b;
 }
 
+
 template<typename Type>
 inline bool
-operator!=(const FixedWidthPointer<Type>& a, void* b)
+operator!=(const FixedWidthPointer<Type>& a, const Type* b)
+{
+	return a.Get() != (addr_t)b;
+}
+
+
+template<typename Type>
+inline bool
+operator==(const FixedWidthPointer<Type>& a, Type* b)
+{
+	return a.Get() == (addr_t)b;
+}
+
+
+template<typename Type>
+inline bool
+operator!=(const FixedWidthPointer<Type>& a, Type* b)
 {
 	return a.Get() != (addr_t)b;
 }

src/system/boot/loader/menu.cpp

@@ -534,7 +534,7 @@ debug_menu_display_current_log(Menu* menu, MenuItem* item)
 static bool
 debug_menu_display_previous_syslog(Menu* menu, MenuItem* item)
 {
-	ring_buffer* buffer = (ring_buffer*)gKernelArgs.debug_output;
+	ring_buffer* buffer = (ring_buffer*)gKernelArgs.debug_output.Pointer();
 	if (buffer == NULL)
 		return true;
 
@@ -595,7 +595,8 @@ save_previous_syslog_to_volume(Directory* directory)
 		return fd;
 	}
 
-	ring_buffer* syslogBuffer = (ring_buffer*)gKernelArgs.debug_output;
+	ring_buffer* syslogBuffer
+		= (ring_buffer*)gKernelArgs.debug_output.Pointer();
 	iovec vecs[2];
 	int32 vecCount = ring_buffer_get_vecs(syslogBuffer, vecs);
 	if (vecCount > 0) {
@@ -899,7 +900,8 @@ add_debug_menu()
 			"Displays the debug info the boot loader has logged.");
 	}
 
-	ring_buffer* syslogBuffer = (ring_buffer*)gKernelArgs.debug_output;
+	ring_buffer* syslogBuffer
+		= (ring_buffer*)gKernelArgs.debug_output.Pointer();
 	if (syslogBuffer != NULL && ring_buffer_readable(syslogBuffer) > 0) {
 		if (!currentLogItemVisible)
 			menu->AddSeparatorItem();

src/system/boot/platform/bios_ia32/smp.cpp

@@ -357,7 +357,7 @@ smp_cpu_ready(void)
 	//TRACE(("smp_cpu_ready: entry cpu %ld\n", curr_cpu));
 
 	preloaded_elf32_image *image = static_cast<preloaded_elf32_image *>(
-		gKernelArgs.kernel_image);
+		gKernelArgs.kernel_image.Pointer());
 
 	// Important.  Make sure supervisor threads can fault on read only pages...
 	asm("movl %%eax, %%cr0" : : "a" ((1 << 31) | (1 << 16) | (1 << 5) | 1));

src/system/boot/platform/bios_ia32/start.cpp

@@ -83,7 +83,7 @@ platform_start_kernel(void)
 		= gKernelArgs.cpu_kstack[0].start + gKernelArgs.cpu_kstack[0].size;
 
 	preloaded_elf32_image *image = static_cast<preloaded_elf32_image *>(
-		gKernelArgs.kernel_image);
+		gKernelArgs.kernel_image.Pointer());
 
 	smp_init_other_cpus();
 	debug_cleanup();

src/system/kernel/arch/x86/timers/x86_hpet.cpp

@@ -221,7 +221,7 @@ hpet_init(struct kernel_args *args)
 		return B_ERROR;
 
 	if (sHPETRegs == NULL) {
-		sHPETRegs = (struct hpet_regs *)args->arch_args.hpet;
+		sHPETRegs = (struct hpet_regs *)args->arch_args.hpet.Pointer();
 		if (vm_map_physical_memory(B_SYSTEM_TEAM, "hpet",
 			(void **)&sHPETRegs, B_EXACT_ADDRESS, B_PAGE_SIZE,
 			B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA,

src/system/kernel/debug/debug.cpp

@@ -1401,8 +1401,10 @@ syslog_init_post_vm(struct kernel_args* args)
 	sSyslogMessage->ident[0] = '\0';
 	//strcpy(sSyslogMessage->ident, "KERNEL");
 
-	if (args->debug_output != NULL)
-		syslog_write((const char*)args->debug_output, args->debug_size, false);
+	if (args->debug_output != NULL) {
+		syslog_write((const char*)args->debug_output.Pointer(),
+			args->debug_size, false);
+	}
 
 	char revisionBuffer[64];
 	length = snprintf(revisionBuffer, sizeof(revisionBuffer),