Symptoms
When you type the object name of an object that is located at a fixed address in the Watch window in the Visual Studio Debugger, you receive a message that resembles the following:
identifier object_name is undefined
For example, this issue can be reproduced by compiling and running the following code on an x86-based system:
Relocate.asm
.586
.MODEL FLAT
PUBLIC _fixed_struct
_fixed_struct = 04000000h
END
Main.cpp
#include <Windows.h>
#define SHM_ADDRESS 0x04000000
#define SHM_SIZE_BYTES 1024
#define SHM_NAME L"TEST_NAME"
extern "C"
{
extern struct fixed_struct_type {
int a;
int b;
int c;
} fixed_struct;
}
void AttachShm()
{
HANDLE mapfile = CreateFileMapping(
INVALID_HANDLE_VALUE, // current file handle (use System page file)
NULL, // default security (not inheritable)
PAGE_READWRITE, // read/write permission
0, // size of File (high-order doubleword)
SHM_SIZE_BYTES, // size of File (low-order doubleword)
SHM_NAME); // name of mapping object
MapViewOfFileEx(
mapfile, // handle to mapping object
FILE_MAP_ALL_ACCESS, // read/write permission
0, // address offset (high-order doubleword)
0, // address offset (low-order doubleword)
SHM_SIZE_BYTES, // size of common block
(LPVOID)SHM_ADDRESS); // suggested starting address
}
int main(int argc, char* argv[])
{
AttachShm();
fixed_struct.a = 30;
// Put a breakpoint on the next line, view fixed_struct.a in watch window
return 0;
}Cause
In earlier versions of Visual Studio, the debugger used relative addresses instead of absolute addresses for all variables. This caused variables that are located at fixed addresses to not be found in the live ranges for the current stack frame.
Resolution
This fix applies only to Visual Studio 2015 Update 3. If you want to view absolute addresses, you must use Visual Studio 2015 Update 3 or a later version.
The fix is available for download from the Microsoft Download Center:
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