Convert 32-bit App To 64-bit

15-09-2021 by

This article applies to the Oracle Developer Studio (previously known as Oracle Solaris Studio) compilers. The principal cause of problems when converting 32-bit applications to 64-bit applications is the change in size of the int type with respect to the long and pointer types. When converting 32-bit programs to 64-bit programs, only long types and pointer types change in size from 32 bits to 64 bits; integers of type int stay at 32 bits in size. This can cause trouble with data truncation when assigning pointer or long types to int types. Also, problems with sign extension can occur when assigning expressions using types shorter than the size of an int to an unsigned long or a pointer. This article discusses how to avoid or eliminate these problems.

Up to now, if you had the 32-bit version of Microsoft 365 Apps installed on a device and you wanted to change to the 64-bit version, you needed to uninstall the existing 32-bit version and then install the 64-bit version. Applies to: Upgrade 32-Bit of OS to 64-Bit so to install and run 64-Bit Programs. As some games or programs may not have the 32-bit version. Or you don't want to waste money to purchase a 32-bit version of the program again. In this case, you can try this way out - to convert the 32-bit operating system to 64-bit.

INSTALATION

Followings are the point to check while converting the 32-bit app to 64-bit. Open the app project in latest Xcode (version = 8) Update project settings to support the iOS version 5.1.1 or later because 64-bit architecture is not supported on version earlier than the iOS 5.1.1. In any case, Windows 10 shows some signs of improvement, at least when it comes to compatibility, even if it’s still not capable of natively running 16-bit apps and games from a 64-bit edition.

Consider the Differences Between the 32-bit and 64-bit Data Models

The biggest difference between the 32-bit and the 64-bit compilation environments is the change in on the previous line. This is useful when you want lint to ignore certain lines of code such as casts and assignments. Exercise extreme care when you use the 'NOTE(LINTED(<optional message>))' comment because it can mask real problems. When you use NOTE, also include #include<note.h>. Refer to the lint man page for more information.

Check for Changes of Pointer Size With Respect to the Size of Plain Integers

Since plain integers and pointers are the same size in the ILP32 compilation environment, 32-bit code commonly relies on this assumption. Pointers are often cast to int or unsigned int for address arithmetic. You can cast your pointers to unsigned long because long and pointer types are the same size in both ILP32 and LP64 data-type models. However, rather than explicitly using unsigned long, use uintptr_t instead because it expresses your intent more closely and makes the code more portable, insulating it against future changes. To use the uintptr_t and intptr_t you need to #include <inttypes.h>.

How To Change 32 Bit App To 64 Bit

Consider the following example:

The following version will function correctly when compiled to both 32-bit and 64-bit targets:

Check for Changes in Size of Long Integers With Respect to the Size of Plain Integers

Because integers and longs are never really distinguished in the ILP32 data-type model, your existing code probably uses them indiscriminately. Modify any code that uses integers and longs interchangeably so it conforms to the requirements of both the ILP32 and LP64 data-type models. While an integer and a long are both 32-bits in the ILP32 data-type model, a long is 64 bits in the LP64 data-type model.

Consider the following example:

Check for Sign Extensions

Sign extension is a common problem when you convert to the 64-bit compilation environment because the type conversion and promotion rules are somewhat obscure. To prevent sign-extension problems, use explicit casting to achieve the intended results.

To understand why sign extension occurs, it helps to understand the conversion rules for ISO C. The conversion rules that seem to cause the most sign extension problems between the 32-bit and the 64-bit compilation environment come into effect during the following operations:

  • Integral promotion

    You can use a char, short, enumerated type, or bit-field, whether signed or unsigned, in any expression that calls for an integer. If an integer can hold all possible values of the original type, the value is converted to an integer; otherwise, the value is converted to an unsigned integer.

  • Conversion between signed and unsigned integers

    When an integer with a negative sign is promoted to an unsigned integer of the same or larger type, it is first promoted to the signed equivalent of the larger type, then converted to the unsigned value.

When the following example is compiled as a 64-bit program, the addr variable becomes sign-extended, even though both addr and a.base are unsigned types.

Convert 32-bit App To 64-bit

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This sign extension occurs because the conversion rules are applied as follows:

  • The structure member a.base is converted from an unsigned int bit field to an int because of the integral promotion rule. In other words, because the unsigned 19-bit field fits within a 32-bit integer, the bit field is promoted to an integer rather than an unsigned integer. Thus, the expression a.base << 13 is of type int. If the result were assigned to an unsigned int, this would not matter because no sign extension has yet occurred.
  • The expression a.base << 13 is of type int, but it is converted to a long and then to an unsigned long before being assigned to addr, because of signed and unsigned integer promotion rules. The sign extension occurs when performing the int to long conversion.

Thus, when compiled as a 64-bit program, the result is as follows:

When compiled as a 32-bit program, the size of an unsigned long is the same as the size of an int, so there is no sign extension.

Check Structure Packing

Check the internal data structures in an applications for holes; that is, extra padding appearing between fields in the structure to meet alignment requirements. This extra padding is allocated when long or pointer fields grow to 64 bits for the LP64 data-type model, and appear after an int that remains at 32 bits in size. Since long and pointer types are 64-bit aligned in the LP64 data-type model, padding appears between the int and long or pointer type. In the following example, member p is 64-bit aligned, and so padding appears between the member k and member p.

Also, structures are aligned to the size of the largest member within them. Thus, in the above structure, padding appears between member i and member j.

Convert 32 Bit Applications To 64 Bit Windows

When you repack a structure, follow the simple rule of moving the long and pointer fields to the beginning of the structure. Consider the following structure definition:

Check for Unbalanced Size of Union Members

64-Bits

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Be sure to check the members of unions because their fields can change size between the ILP32 and the LP64 data-type models, making the size of the members different. In the following union, member _d and member array _l are the same size in the ILP32 model, but different in the LP64 model because long types grow to 64 bits in the LP64 model, but double types do not.

Convert 32-bit App To 64-bit

The size of the members can be rebalanced by changing the type of the _l array member from type long to type int.

Make Sure Constant Types are Used in Constant Expressions

A lack of precision can cause the loss of data in some constant expressions. Be explicit when you specify the data types in your constant expression. Specify the type of each integer constant by adding some combination of { u,U,l,L}. You can also use casts to specify the type of a constant expression. Consider the following example:

The above code can be made to work as intended, by appending the type to the constant, 1, as follows:

How To Change 32 Bit Software To 64 Bit

Check Format String Conversions

Make sure the format strings for printf(3S), sprintf(3S), scanf(3S), and sscanf(3S) can accommodate long or pointer arguments. For pointer arguments, the conversion operation given in the format string should be %p to work in both the 32-bit and 64-bit compilation environments. For long arguments, the long size specification, l, should be prepended to the conversion operation character in the format string.

Also, check to be sure that buffers passed to the first argument in sprintf contain enough storage to accommodate the expanded number of digits used to convey long and pointer values. For example, a pointer is expressed by 8 hex digits in the ILP32 data model but expands to 16 in the LP64 data model.

Type Returned by sizeof() Operator is an unsigned long

In the LP64 data-type model, sizeof() has the effective type of an unsigned long. If sizeof() is passed to a function expecting an argument of type int, or assigned or cast to an int, the truncation could cause a loss of data. This is only likely to be problematic in large database programs containing extremely long arrays.

Use Portable Data Types or Fixed Integer Types for Binary Interface Data

Convert 32-bit App To 64-bit

For data structures that are shared between 32-bit and 64-bit versions of an application, stick with data types that have a common size between ILP32 and LP64 programs. Avoid using long data types and pointers. Also, avoid using derived data types that change in size between 32-bit and 64-bit applications. For example, the following types defined in <sys/types.h> change in size between the ILP32 and LP64 data models:

  • clock_t, which represents the system time in clock ticks
  • dev_t, which is used for device numbers
  • off_t, which is used for file sizes and offsets
  • ptrdiff_t, which is the signed integral type for the result of subtracting two pointers
  • size_t, which reflects the size, in bytes, of objects in memory
  • ssize_t, which is used by functions that return a count of bytes or an error indication
  • time_t, which counts time in seconds

Using the derived data types in <sys/types.h> is a good idea for internal data, because it helps to insulate the code from data-model changes. However, preccisely because the size of these types are prone to change with the data model, using them is not recommended in data that is shared between 32-bit and 64-bit applications, or in other situations where the data size must remain fixed. Nevertheless, as with the sizeof() operator discussed above, before making any changes to the code, consider whether the loss of precision will actually have any practical impact on the program.

For binary interface data, consider using the fixed-width integer types in <inttypes.h>. These types are good for explicit binary representations of the following:

  • Binary interface specifications
  • On-disk data
  • Over the data wire
  • Hardware registers
  • Binary data structures

Check for Side Effects

Be aware that a type change in one area can result in an unexpected 64-bit conversion in another area. For example, check all the callers of a function that previously returned an int and now returns an ssize_t.

Consider the Effect of long Arrays on Performance

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Large arrays of long or unsigned long types, can cause serious performance degradation in the LP64 data-type model as compared to arrays of int or unsigned int types. Large arrays of long types cause significantly more cache misses and consume more memory. Therefore, if int works just as well as long for the application purposes, it's better to use int rather than long. This is also an argument for using arrays of int types instead of arrays of pointers. Some C applications suffer from serious performance degradation after conversion to the LP64 data-type model because they rely on many, large, arrays of pointers.

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