Seven Steps of Migrating a Program to a 64-bit System

Seven Steps of Migrating a Program to a
64-bit System
Author: Andrey Karpov

Date: 19.04.2009

Abstract
The article describes the main steps which should be performed to correctly port 32-bit Windows
applications on 64-bit Windows systems. Although the article is meant for developers using C/C++ in
Visual Studio 2005/2008 environment, it will be also useful for other developers who plan to port their
applications on 64-bit systems.

Introduction
The article describes the main problems facing developers who plan to port 32-bit programs on 64-bit
systems. Of course the list of the issues considered is not complete, but we hope that we'll offer a more
detailed version of this article in future. The author would be glad to receive responses, comments and
questions which will help increase information value of this article.

1. The first step. 64-bit mode can be different. Let's sort it out
Within the framework of a computer architecture by the term "64-bit" 64-bit integers and other 64-bit-
sized data types are understood. By "64-bit" systems 64-bit microprocessor architectures (for example,
EM64T, IA-64) or 64-bit operation system (for example, Windows XP Professional x64 Edition) can be
understood [1].

AMD64 (or x86-64, Intel 64, EM64T, x64) is a 64-bit microprocessor architecture and a corresponding set
of instructions developed by AMD company [2]. This set of instructions was licensed by Intel company
under the name of EM64T (Intel64). AMD64 architecture is an extension of x86 architecture with full
backward compatibility. The architecture became widespread as a basis of personal computers and
workstations.

IA-64 is a 64-bit microprocessor architecture developed together by Intel and Hewlett Packard
companies [3]. It is implemented in microprocessors Itanium and Itanium 2 [4]. The architecture is used
mainly in multi-processor servers and cluster systems.

AMD64 and IA-64 are two different 64-bit architectures incompatible with each other. That's why
developers have to decide at once if they need support of the both architectures or only one of them. In
most cases, if you don't develop highly tailored software for cluster systems or don't implement your
own high-performance DBMS, most likely you will have to implement support only of AMD64
architecture which is much more popular than IA-64. It especially concerns software for PC market
which is nearly 100% occupied by AMD64 architecture.

Further in the article we'll speak only about AMD64 (EM64T, x64) architecture, as nowadays it is the
most topical for application software developers.

Speaking about different architectures we should mention the notion "Data model". By a data model we
understand correlations between type sizes accepted within the framework of the development
environment. There can be several development tools sticking to different data types for one operation
system. But usually only one model dominates which corresponds to the hardware and software
environment most. Such an example is 64-bit Windows whose original data model is LLP64. But for
compatibility purposes 64-bit Windows supports execution of 32-bit programs which operate in ILP32LL
data model mode. Table 1 gives information about the basic data models.

Table 1. Data models.

A data model being used influences the process of developing 64-bit applications as you need to keep in
mind sizes of the data being used in programs' code [5].

2. The second step. Find out if you need the 64-bit version of your
product
You should begin mastering 64-bit systems with the question: "Do I really need to rebuild my project for
a 64-bit system?" You give an answer to this question but only after you have thought it over, without
hurry. On the one hand, you can lag behind your rivals if you don't offer 64-bit solutions. On the other
hand, you can just waste your time developing a 64-bit application which won't provide any competitive
advantages.

Let's list the basic factors that will help you make up your mind.

2.1. Applications' life-cycle duration
You shouldn't create the 64-bit version of an application with a short life-cycle. Thanks to WOW64
subsystem old 32-bit applications operate rather well on 64-bit Windows systems and that's why there
is no sense in making a program 64-bit for it won't be supported in 2 years [6]. Moreover, practice
shows that porting on 64-bit Windows versions has been delayed and perhaps most of your users will
use only the 32-bit version of your program solution in near-term outlook.

If you plan long-term development and support of a program product, you should begin to work over
the 64-bit version of your solution. You can do this without hurry but keep in mind that the longer you
don't have a complete 64-bit version, the more difficulties you will face in supporting this application
installed on 64-bit Windows versions.

2.2. Resource-intensiveness of an application
Recompilation of a program for a 64-bit system will allow it to use large sizes of main memory and will
also speed up its operation by 5-15%. Increase in 5-10% will be gained due to using the 64-bit
processor's architectural abilities, for example a larger number of registers. The rest speed increase in 1-
5% is explained by absence of WOW64 layer which translates API calls between 32-bit applications and a
64-bit operation system.

If your program doesn't operate with large data sizes (more than 2GB) and the speed of its operation is
not crucial, porting on a 64-bit system is not so urgent in the near future.

By the way, even simple 32-bit applications can get advantage being launched in 64-bit environment.
Perhaps you know that a program built with /LARGEADDRESSAWARE:YES key can allocate up to 3 GB of
memory if the 32-bit Windows is launched with /3gb key. This very 32-bit program launched on a 64-bit
system can allocate nearly 4 GB of memory (in practice about 3.5 GB).

2.3. Development of libraries
If you develop libraries, components or other elements with the help of which third-party developers
create their software you should act quickly while creating the 64-bit version of your product.
Otherwise, your clients interested in release of 64-bit versions will have to search for alternative
solutions. For example, some developers of software-hardware security responded with a large delay to
appearance of 64-bit programs and that made some clients search for other tools to protect their
programs.

An additional advantage of releasing the 64-bit version of a library is that you can sell it as a separate
product. Thus, your clients wishing to create both 32-bit and 64-bit applications will have to buy 2
different licenses. For example, this policy is used by Spatial Corporation when selling Spatial ACIS
library.

2.4. Dependence of your product on third-party libraries
Before you plan your work on creation of the 64-bit version of your product, find out if there are 64-bit
versions of libraries and components used in it. Besides, learn about the pricing policy concerning the
64-bit version of a library. If there is no support provided, search for alternative solutions supporting 64-
bit systems beforehand.

2.5. Using 16-bit applications
If your solutions still use 16-bit units it is high time you got rid of them. 16-bit applications in 64-bit
Windows versions are not supported.

We should explain one thing here concerning using 16-bit installers. They are still used to install some
32-bit applications. There is a special mechanism which replaces some of the most popular 16-bit
installers with their newer versions. It can cause a false opinion that 16-bit programs still operate in 64-
bit environment. Remember: it is not so.

2.6. Assembler code
Don't forget that using a large size of Assembler code can significantly increase the cost of creating the
64-bit version of an application.

Having thought all the listed factors over and weighed all pros and cons, decide if you need to port your
project on 64-bit systems. If yes, we go further.

3. The third step. Toolkit
If you have decided to develop the 64-bit version of your product and are ready to spend time on it, it is
still not enough to guarantee success. The point is that you must possess the entire necessary toolkit
and here you can face some difficulties.

Absence of a 64-bit compiler can be the simplest but the most insuperable problem. The article is being
written in 2009 but there is still no 64-bit C++ Builder compiler by Codegear [7]. Its release is expected
by the end of this year. It is impossible to avoid this problem, if only to rewrite the whole project using,
for example, Visual Studio. But if everything is clear about absence of a 64-bit compiler, other similar
problems can appear to be less transparent and occur only at the stage of porting the project on a new
architecture. That's why we would like to advise you to find out beforehand if there are all the necessary
components you will need to implement the 64-bit version of your product. You may face unpleasant
surprises.

Of course it is impossible to list everything you may need for a project here, but I will continue the list
which will help you to orient yourself and perhaps to remember about other things necessary to
implement your 64-bit project:

3.1. A 64-bit compiler
There is hardly more to say about the importance of having a 64-bit compiler. It simply must be.

If you are planning to develop 64-bit applications using the latest (by the moment the article is written)
Visual Studio 2008 version, the following Table 2 will help you understand which of the Visual Studio
editions you need.

Table 2. Abilities of different editions of Visual Studio 2008.

3.2. 64-bit computers under control of 64-bit operation system
Of course you can use virtual machines for launching 64-bit applications on 32-bit computers but it is
too inconvenient and won't provide the necessary level of tests. It is desirable that the machines have
not less than 4-8 GB of main memory.

3.3. 64-bit versions of all the used libraries
If libraries are presented in source codes, there must be a 64-bit configuration of the project. It can be a
thankless and difficult task to update the library for a 64-bit system on your own, and the result can be
unreliable and contain errors. Besides, you can violate license agreements by these actions. If you use
libraries in the form of binary units you should also find out if there are 64-bit units. You cannot use 32-
bit DLL inside a 64-bit application. You can create a special tie through COM but it will be a separate
large and difficult task [8]. Also keep in mind that you may need to spend some extra money to purchase
the 64-bit version of the library.

3.4. Absence of embedded Assembler code
Visual C++ doesn't support a 64-bit inline assembler. You must either use an external 64-bit assembler
(for example, MASM) or possess an implementation with the same functionality in C/C++ [9].

3.5. Testing methodology update
It means considerable remaking of the testing methodology, update of unit-tests and using new tools.
We will speak about it in more detail further, but don't forget to take it into account at the stage of
evaluating time costs on migration of an application on a new system [10].

3.6. New data for testing
If you are developing resource-intensive applications using a large size of main memory, you need to
provide replenishment of the testing input data base. At load testing of 64-bit applications it is desirable
to excess the limits of 4 GB of the used memory. Many errors can occur only in these conditions.

3.7. 64-bit security systems
The security system being used must provide full support of 64-bit systems. For example, Aladdin
company has released 64-bit drivers for support of hardware Hasp keys rather quickly. But for a long
time there has been no system of automatic protection of 64-bit binary files (Hasp Envelop program).
Thus, the security mechanism had to be implemented manually inside the program code and that was
one more difficult task demanding professionalism and time. Don't forget about such things relating to
security, update system etc.

3.8. Installer
You need a new installer able to fully install 64-bit applications. We would like to warn you about one
very typical mistake. It is creation of 64-bit installers for installing 32/64-bit program products. Preparing
the 64-bit version of an application developers often want to make "64-bit mode" in it absolute and
create a 64-bit installer forgetting that those who use a 32-bit operation system won't simply be able to
launch such an installation package. Pay attention that it is not the 32-bit application included into the
distribution kit together with the 64-bit one, but the installer itself. For if the distribution kit is a 64-bit
application, of course it won't operate on a 32-bit operation system. What is the most unpleasant is that
a user won't be able to guess why it happens. He will simply see the installation package which cannot
be launched.

4. The fourth step. Setting of a project in Visual Studio 2005/2008
Creation of the 64-bit configuration of a project in Visual Studio 2005/2008 looks rather simple.
Difficulties will begin at the stage of building a new configuration and searching errors in it. To create
the 64-bit configuration itself you just need to perform the following 4 steps:

Launch the configuration manager as shown in Figure 1:

Figure 1. Launch of the configuration manager.

In the configuration manager choose support of the new platform (Figure 2):

Figure 2. Creation of a new configuration.

Choose the 64-bit platform (x64) and as a basis - settings from the 32-bit version (Figure 3). Those
settings which influence the building mode will be corrected by Visual Studio automatically.

Figure 3. Choose x64 as a platform and use Win32 configuration as a basis.

Addition of a new configuration is complete and now you can choose the 64-bit configuration version
and begin compiling a 64-bit application. Choosing the 64-bit configuration for building is shown in
Figure 4.

Figure 4. Now both 32-bit and 64-bit configurations are available.

If you are lucky you won't need to additionally set a 64-bit project. But it greatly depends on the project,
its complexity and the number of libraries used. The only thing you should change at once is the stack's
size. In case if the stack's size in your project is set by default, that is 1 MB, you should define it as 2 MB
for the 64-bit version. It is not necessary but it is better to insure yourself beforehand. If you use the size
different from that by default, there is sense in increasing it twice for the 64-bit version. To do this find
and change Stack Reserve Size and Stack Commit Size parameters in the project's settings.

5. The fifth step. Compilation of an application
Here we should tell you about typical problems occurring at the stage of compiling the 64-bit
configuration, discuss what problems occur in third-party libraries, tell you that in the code relating to
WinAPI functions the compiler won't permit placing of a pointer into LONG type and you will have to
update your code and use LONG_PTG type. And there is a lot else to say. Unfortunately, there are so
many problems and errors are so various that we cannot describe them all in one article and even book.
You will have to look through all the errors the compiler will show you and all the new warnings which
haven't been there before by yourself and in each particular case to find out how to update the code.

The following list of links to resources devoted to developing 64-bit applications can partly help you:
http://www.viva64.com/links/64-bit-development/. The list is constantly enlarged and the author will
be glad if readers send him links to resources which are, in their opinion, worthy attention.

Let's describe here only types which can be of interest for developers when porting applications. These
types are shown in Table 3. Most recompilation errors will relate to using these very types.

Type Type's size on Note
x86 / x64
platform
int 32 / 32 Basic type. On 64-bit systems remains 32-bit.
long 32 / 32 Basic type. On 64-bit Windows systems remains 32-bit. Keep in mind
that in 64-bit Linux systems this type was extended to 64-bit. Don't
forget about it if you develop code which should be compiled for
Windows and Linux systems.
size_t 32 / 64 Basic unsigned type. The type's size is chosen in such a way that you
could write the maximum size of a theoretically possible array into it.
You can safely put a pointer into size_t type (except for pointers to
class functions, but this is a special case).
ptrdiff_t 32 / 64 Similar to size_t type but this is a signed type. The result of the
expression where one pointer is subtracted from the other (ptr1-ptr2)
will have ptrdiff_t type.
Pointer 32 / 64 The size of the pointer directly depends on the platform's size. Be

careful while converting pointers to other types.
__int64 64 / 64 Signed 64-bit type.
DWORD 32 / 32 32-bit unsigned type. In WinDef.h is defined as:
typedef unsigned long DWORD;
DWORDLONG 64 / 64 64-bit unsigned type. In WinNT.h is defined as:
typedef ULONGLONG DWORDLONG;
DWORD_PTR 32 / 64 Unsigned type in which a pointer can be placed. In BaseTsd.h is defined
as:
typedef ULONG_PTR DWORD_PTR;
DWORD32 32 / 32 32-bit unsigned type. In BaseTsd.h is defined as:
typedef unsigned int DWORD32;
DWORD64 64 / 64 64-bit unsigned type. In BaseTsd.h is defined as:
typedef unsigned __int64 DWORD64;
HALF_PTR 16 / 32 A half of a pointer. In Basetsd.h is defined as:
#ifdef _WIN64
typedef int HALF_PTR;
#else
typedef short HALF_PTR;
#endif
INT_PTR 32 / 64 Signed type in which a pointer can be placed. In BaseTsd.h is defined
as:
#if defined(_WIN64)
typedef __int64 INT_PTR;
#else
typedef int INT_PTR;
#endif
LONG 32 / 32 Signed type which remained 32-bit. That's why in many cases
LONG_PTR now should be used. In WinNT.h is defined as:
typedef long LONG;
LONG_PTR 32 / 64 Signed type in which a pointer can be placed. In BaseTsd.h is defined
as:
#if defined(_WIN64)
typedef __int64 LONG_PTR;
#else
typedef long LONG_PTR;
#endif
LPARAM 32 / 64 Parameter for sending messages. In WinNT.h is defined as:
typedef LONG_PTR LPARAM;
SIZE_T 32 / 64 Analog of size_t type. In BaseTsd.h is defined as:
typedef ULONG_PTR SIZE_T;
SSIZE_T 32 / 64 Analog of ptrdiff_t type. In BaseTsd.h is defined as:
typedef LONG_PTR SSIZE_T;
ULONG_PTR 32 / 64 Unsigned type in which a pointer can be placed. In BaseTsd.h is defined
as:
#if defined(_WIN64)
typedef unsigned __int64 ULONG_PTR;
#else
typedef unsigned long ULONG_PTR;
#endif
WORD 16 / 16 Unsigned 16-bit type. In WinDef.h is defined as:
typedef unsigned short WORD;
WPARAM 32 / 64 Parameter for sending messages. In WinDef.h is defined as:
typedef UINT_PTR WPARAM;

Table N3. Types to be noted while porting 32-bit programs on 64-bit Windows systems.

6. Diagnosis of hidden errors
If you think that after correcting all the compilation errors you will get a long-expected 64-bit application
we have to disappoint you. The most difficult is just ahead. At the stage of compilation you will correct
the most explicit errors which the compiler had managed to detect and which mostly relate to
impossibility of implicit type conversion. But this is only a small part of the problem. Most errors are
hidden. From the viewpoint of the abstract C++ language these errors look safe and are disguised by
explicit type conversions. The number of such errors is much larger than the number of errors detected
at the stage of compilation.

You shouldn't set your hopes on /Wp64 key. This key is often presented as a wonderful means of
searching 64-bit errors. In reality /Wp64 key just allows you to get some warning messages concerning
incorrectness of some code sections in 64-bit mode while compiling 32-bit code. While compiling 64-bit
code these warnings will be shown anyway. And that's why /Wp64 key is ignored when compiling a 64-
bit application. And surely this key won't help in search of hidden errors [11].

Let's consider several examples of hidden errors.

6.1. Explicit type conversion
The simplest but none the easiest for detection error class relates to explicit type conversions when
significant bits are cut. A popular example is conversion of pointers to 32-bit types when transferring
them into functions such as SendMessage:

MyObj* pObj = ...

::SendMessage(hwnd, msg, (WORD)x, (DWORD)pObj);

Here the explicit type conversion is used to turn a pointer into a numeric type. For a 32-bit architecture
this example is correct as the last parameter of SendMessage function has LPARAM type which
coincides with DWORD on a 32-bit architecture. For a 64-bit architecture DWORD is incorrect and must
be replaced with LPARAM. LPARAM type has sizes of 32 or 64 bits depending on the architecture.

This is a simple case but type conversion often looks more complicated and it is impossible to detect it
using the compiler's warnings or search through the program text. Explicit type conversions suppress
the compiler's diagnosis as they are intended for this very purpose - to tell the compiler that the type
conversion is correct and the programmer is responsible for the code's safety. Explicit search won't help
as well. Types can have non-standard names (defined by the programmer through typedef), and the
number of methods to perform explicit type conversion is also large. To safely diagnose such errors you
must use only a special toolkit such as Viva64 or PC-Lint analyzers.

6.2. Implicit type conversion
The next example relates to implicit type conversion when significant bits are also lost. fread function's
code performs reading from the file but it is incorrect when trying to read more than 2 GB on a 64-bit
system.

size_t __fread(void * __restrict buf, size_t size,

size_t count, FILE * __restrict fp);

size_t

fread(void * __restrict buf, size_t size, size_t count,

FILE * __restrict fp)

{

int ret;

FLOCKFILE(fp);

ret = __fread(buf, size, count, fp);

FUNLOCKFILE(fp);

return (ret);

}

__fread function returns size_t type but int type is used to store the number of the bytes read. As a
result at large sizes of read data the function can return a false number of bytes.

You can say that it is an illiterate code for beginners, that the compiler will announce about this type
conversion and that this code is actually easy to find and to correct. This is in theory. And in practice
everything may be quite different in cases of large projects. This example is taken from FreeBSD source
code. The error was corrected only in December 2008! Note that the first (experimental) 64-bit version
of FreeBSD was released in June 2003.

This is the source code before it has been corrected:

http://www.viva64.com/go.php?url=503

And this is the corrected variant (December 2008):


6.3. Bits and shifts
It is easy to make an error in the code while working with separate bits. The following error type relates
to shift operations. Here is an example:

ptrdiff_t SetBitN(ptrdiff_t value, unsigned bitNum) {

ptrdiff_t mask = 1 << bitNum;

return value | mask;

}

This code works well on a 32-bit architecture and allows you to set bits with numbers 0 to 31 to unity.
After porting the program on a 64-bit platform you will need to set bits 0 to 63. But this code will never
set bits 32-63. Pay attention that "1" has int type and when a shift at 32 positions occurs an overflow
will take place as shown in Figure 5. Whether we will get 0 (Figure 5-B) or 1 (Figure 5-C), as a result,
depends on the compiler's implementation.

Figure 5. A - Correct setting of the 32th bit in 32-bit code; B,C - error of setting of the 32th bit on a 64-bit
system (two ways of behavior)

To correct the code we need to make "1" constant of the same type as mask variable:

ptrdiff_t mask = ptrdiff_t(1) << bitNum;

Also pay attention that the incorrect code leads to one more error. When setting 31 bits on a 64-bit
system the result of the function will be the value 0xffffffff80000000 (see Figure 6). The result of 1 << 31
expression is the negative number -2147483648. In a 64-bit integer variable this number is presented as
0xffffffff80000000.

Figure 6. Error of setting of the 31th bit on a 64-bit system

6.4. Magic numbers
Magic constants, i.e. numbers with the help of which the size of this or that type is defined, can cause a
lot of troubles. A proper decision is to use sizeof() operators for these purposes, but in a large program
an old code section can still be hidden where, as programmers believe, the pointer's size is 4 bytes and
in size_t it is always 32 bits. Usually such errors look as follows:

size_t ArraySize = N * 4;

size_t *Array = (size_t *)malloc(ArraySize);

Figure 4 shows the basic numbers with which you should work with caution while migrating on a 64-bit
platform.

Table 4. Basic magic values which are dangerous while porting applications from a 32-bit platform to a
64-bit one.

6.5. Errors relating to using 32-bit variables as indexes
In programs processing large data sizes errors relating to indexing large arrays or eternal loops may
occur. The following example contains 2 errors:

const size_t size = ...;

char *array = ...;

char *end = array + size;

for (unsigned i = 0; i != size; ++i)

{

const int one = 1;

end[-i - one] = 0;

}

The first error consists in that if the size of the data being processed excesses 4 GB (0xFFFFFFFF) an
eternal loop may occur as 'i' variable has 'unsigned' type and will never reach 0xFFFFFFFF value. I write
deliberately that it can occur but not necessarily. It depends on what code the compiler will build. For
example, in debug mode the eternal loop will be present and in release-code there will be no loop as the

compiler will decide to optimize the code using a 64-bit register for the counter and the loop will be
correct. All this adds much confusion and the code which worked yesterday can fail to work today.

The second error relates to parsing the array from beginning to end for what negative indexes' values
are used. This code will operate well in 32-bit mode but when executed on a 64-bit computer access
outside the array's limits will occur at the first iteration of the loop, and there will be a program crash.
Let's study the reason of such a behavior.

According to C++ rules "-i - one" expression on a 32-bit system will be calculated as follows: (at the first
step i = 0):

"-i" expression has unsigned type and has 0x00000000u value.

'one' variable will be extended from 'int' type to unsigned type and will equal 0x00000001u. Note: int
type is extended (according to C++ standard) up to 'unsigned' type if it participates in an operation
where the second argument has unsigned type.

A subtraction operation takes place in which two values of unsigned type participate and the result of
the operation equals 0x00000000u - 0x00000001u = 0xFFFFFFFFu. Note that the result will have
unsigned type.

On a 32-bit system access to the array by the index 0xFFFFFFFFu is the same as using -1 index. That is
end[0xFFFFFFFFu] is an analog of end[-1]. As a result the array's items will be processed correctly.

In a 64-bit system the situation will be quite different concerning the last point. Unsigned type will be
extended to signed ptfdiff_t type and the array's index will equal 0x00000000FFFFFFFFi64. As a result an
overflow will occur.

To correct the code you should use ptrdiff_t and size_t types.

6.6. Errors relating to change of the types of the used functions
There are errors which are nobody's fault but they are still errors. Imagine that long long ago in a
faraway galaxy (in Visual Studio 6.0) a project was developed which contained CSampleApp class - a
successor of CWinApp. In the basic class there is a virtual function WinHelp. The successor overlaps this
function and performs all the necessary actions. This process is shown in Figure 7.

Figure 7. Efficient correct code created in Visual Studio 6.0

After that the project is ported on Visual Studio 2005 where the prototype of WinHelp function has
changed but nobody will notice it because in 32-bit mode DWORD and DWORD_PTR types coincide and
the program continues operating correctly (Figure 8).

Figure 8. Incorrect but efficient 32-bit code

After that the project is ported on Visual Studio 2005 where the prototype of WinHelp function has
changed but nobody will notice it because in 32-bit mode DWORD and DWORD_PTR types coincide and
the program continues operating correctly (Figure 8).

Figure 9. The error occurs in 64-bit code

6.7. Diagnosis of hidden errors
There are a lot of examples of such 64-bit errors. Those who are interested in this topic and would like
to know more about these errors see the article "20 issues of porting C++ code on the 64-bit platform"
[12].

As you see the stage of searching hidden errors is a nontrivial task, and besides, many of them will occur
irregularly and only at large input data. Static code analyzers are good for diagnosing such errors as they
can check the whole code of an application independently from the input data and the frequency of its
sections' execution in real conditions. There is sense in using static analysis both at the stage of porting
an application on 64-bit platforms to find most errors at the very beginning and in further development

of 64-bit solutions. Static analysis will warn and teach a programmer to better understand the
peculiarities of errors relating to a 64-bit architecture and to write more efficient code. The author of
the article is a developer of one of such specialized code analyzers named Viva64 [13]. To learn more
about the tool and to download a demo version visit the site of OOO "Program Verification Systems"
company.

For justice' sake we should say that Gimpel PC-Lint and Parasoft C++test code analyzers have sets of
rules for diagnosing 64-bit errors. But, firstly, these are general-purpose analyzers and the rules of
diagnosing 64-bit errors are incomplete. Secondly, they are intended mostly for LP64 data model used in
the family of Linux operation system and that's why they are not so useful for Windows programs where
LLP64 data model is used [14].

7. The seventh step. Update of the testing process
The step of searching errors in program code described in the previous section is necessary but
insufficient. None of the methods, including static code analysis, can guarantee detection of all the
errors, and the best result can be achieved only when combining different methods.

If your 64-bit program processes a larger data size than the 32-bit version, you need to extend tests to
include processing data with the size more than 4 GB. This is the border beyond which many 64-bit
errors begin to occur. Such tests may take much more time and you must be prepared for it. Usually
tests are written in such a way that each test could process a small number of items and thus make it
possible to perform all the internal unit-tests in several minutes while automatic tests (for example,
using AutomatedQA TestComplete) could be performed in several hours. It is nearly absolutely certain
that the sorting function sorting 100 items will behave correctly at 100000 items on a 32-bit system. But
the same function can fail on a 64-bit system while trying to process 5 billion items. The speed of
executing a unit-test can fall in million times. Don't forget about the cost of adapting tests while
mastering 64-bit systems. A good solution is to divide unit-tests into quick (working with small memory
sizes) and slow ones processing gigabytes and executed, for example, in the nighttime. Automated
testing of resource-intensive 64-bit programs can be organized on the basis of distributed calculations.

There is one more unpleasant thing. You will hardly succeed in using tools like BoundsChecker for
searching errors in resource-intensive 64-bit programs consuming large memory size. The reason is a
great slowdown of the programs being tested what makes this approach very inconvenient. In the mode
of diagnosing all the errors relating to memory operation, Parallel Inspector tool included into Intel
Parallel Studio will slow down execution of an application in 100 times on the average (Figure 10). It is
very likely that you will have to leave the algorithm being tested for the night to see the results only the
next day while normally this algorithm operates just 10 minutes. And still I'm sure that Parallel Inspector
is one of the most useful and convenient tools when working in the mode of searching memory-
operation errors. You just must be ready to change the practice of error diagnosing and keep it in mind
when planning to master 64-bit systems.

Figure 10. The settings window of Parallel Inspector program before launching an application.

And the last thing. Don't forget to add tests checking compatibility of data formats between the 32-bit
and 64-bit versions. Data compatibility is often violated during migration because of writing of such
types as size_t or long (in Linux systems) into files.

References
1. Wikipedia. 64-bit. http://www.viva64.com/go.php?url=203
2. Wikipedia. AMD64. http://www.viva64.com/go.php?url=220
3. Sverre Jarp. IA-64 architecture. A Detailed Tutorial. http://www.viva64.com/go.php?url=222
4. Wikipedia. Itanium. http://www.viva64.com/go.php?url=221
5. Andrey Karpov. The forgotten problems of 64-bit programs development
http://www.viva64.com/art-1-2-16511733.html
6. Wikipedia. WOW64. http://www.viva64.com/go.php?url=207
7. Nick Hodges. The Future of the Delphi Compiler. http://www.viva64.com/go.php?url=208
8. Mike Becker. Accessing 32-bit DLLs from 64-bit code. http://www.viva64.com/go.php?url=209
9. Eric Palmer. How to use all of CPUID for x64 platforms under Microsoft Visual Studio .NET 2005.
10. Andrey Karpov, Evgeniy Ryzhkov. Traps detection during migration of C and C++ code to 64-bit
Windows. http://www.viva64.com/art-1-2-2140958669.html
11. Andrey Karpov. 64 bits, /Wp64, Visual Studio 2008, Viva64 and all the rest...

12. Andrey Karpov, Evgeniy Ryzhkov. 20 issues of porting C++ code on the 64-bit platform.
13. Evgeniy Ryzhkov. Viva64: what is it and who is it for? http://www.viva64.com/art-1-2-
903037923.html
14. Andrey Karpov. Comparison of analyzers' diagnostic possibilities at checking 64-bit code.

Seven Steps of Migrating a Program to a 64-bit System

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