Category : C Source Code
Archive   : BCPPTECH.ZIP
Filename : TI728.ASC

PRODUCT : Borland C++ NUMBER : 728
VERSION : 2.0
OS : DOS
DATE : February 25, 1992 PAGE : 1/6

TITLE : Issues with Petzold's Programming Windows and Borland
C++




COMPILING IN C++
----------------
When using Borland C++, problems with the examples from Charles
Petzold's Programming Windows will often result from compiling
them unmodified in C++ mode. Here are some symptoms of this
problem which you may run across when compiling the examples from
Programming Windows:

1. HELLOWIN example does not display the text until it is
painted a second time

2. KEYLOOK example hangs with hourglass

3. CLOVER example does not print anything

4. GetSystemMetrics (or other API functions) give unusual
results

The quick and obvious solution to this problem is to switch the
compiler back to C mode. However, it IS quite possible to
compile these programs in C++ by making some minor modifications.

The Petzold DEF files do not contain the C++ name mangled names
for the exported functions. If the programs are to be compiled
as C++, the _export modifier should be used for any functions to
be exported. The function entries in the EXPORTS section of the
DEF file can then be removed. Following this method, the
declaration for a sample exported function would be:

long FAR PASCAL _export WndProc (HWND, WORD, WORD, LONG) ;

An alternative way to export the functions would be to leave the
EXPORTS entry in the DEF file as is and declare the function as
extern "C" in the C++ source code. This will "turn off" name
mangling for that function and thus the identifier for that
function will match the one exported in the DEF file. Following
this method, the declaration for a sample exported function would
be:

extern "C" long FAR PASCAL WndProc (HWND, WORD, WORD, LONG) ;

COMPILING IN C
--------------












PRODUCT : Borland C++ NUMBER : 728
VERSION : 2.0
OS : DOS
DATE : February 25, 1992 PAGE : 2/6

TITLE : Issues with Petzold's Programming Windows and Borland
C++




The same symptoms described in the section above can occur when
compiling in C mode if you have not included the program's .DEF
file when linking your program. If you are using BC or BCX, this
means you need to have a project file that includes your .DEF
file in addition to your .C file (and .RC file if one exists).
If you are using BCC or BCCX and calling TLINK directly, this
means that you have forgotten to include the .DEF file on your
TLINK command line. See the Borland C++ User's Guide for more
information on TLINK.

SYSMETS EXAMPLE
---------------
In the SYSMETS2 example (page 73), max and min can return
incorrect values because NUMLINE returns an unsigned int rather
than an int.

The problem has to do with the NUMLINES macro defined at the top
of SYSMETS.H (page 59). As required by ANSI, sizeof returns an
unsigned. This, combined with the max and min macros, results in
nVscrollPos never appearing to be less than 0. Changing the
NUMLINES macro to:

#define NUMLINES ((int)sizeof sysmetrics/(int) sizeof sysmetrics[0])

will resolve this problem.

In addition, it should be noted that the max and min macros are
not defined in the C++ language. The reason for this omission is
to allow C++ programmers to overload the function names min and
max. To compile this example as C++, the min and max macros
should be copied from windows.h directly into the SYSMETS2.C
source file.

DDEPOP / SHOWPOP EXAMPLE
------------------------
Line 573 of DDEPOP.C declares a character array in the function
PostDataMessage as follows:

char szPopulation [10];

This line should read:

char szPopulation [11];












PRODUCT : Borland C++ NUMBER : 728
VERSION : 2.0
OS : DOS
DATE : February 25, 1992 PAGE : 3/6

TITLE : Issues with Petzold's Programming Windows and Borland
C++




Without this modification, a UAE will occur when running its
client program SHOWPOP.EXE.

Note that there is a similar declaration on line 239 in the
function ServerProc. Do not confuse this declaration with the
one on line 573. Since the array szPopulation is never used in
the function ServerProc, you may remove the declaration of
szPopulation from line 239.

BTNLOOK EXAMPLE
---------------
On line 24 of BTNLOOK.C, change BS_USERBUTTON to BS_OWNERDRAW.
BS_USERBUTTON is not a style documented by Microsoft for
Microsoft Windows 3.0.

READ VERSUS _LREAD
------------------
Microsoft Windows defines a set of functions for file management
which are separate from the file management functions used in
traditional DOS applications. Microsoft C 6.0 happens to allow
the free mixture of Windows file handles created with OpenFile()
and standard DOS file handles created with open(). This
"feature" is undocumented and therefore not standard Windows
programming. In Borland C++, Windows file handles and DOS file
handles are not the same and cannot be freely mixed in calls to
functions.

Some of the Programming Windows examples make calls to OpenFile()
and use the resulting handle in a call to read(). To make such
examples work when compiling with Borland C++, it will be
necessary to commit your program to one system of file management
or the other. If you choose to use OpenFile(), calls to read()
and write() should be converted to calls to _lread() and
_lwrite(). If you choose to continue with calls to read()
and write(), the call to OpenFile should be converted to a call
to open().

MAKE FILES
----------
The make files provided for the examples in Programming Windows
were designed with Microsoft C in mind and are not compatible
with Borland C++. Here is an example Borland makefile which can
be used for the simpler single file Windows programs.












PRODUCT : Borland C++ NUMBER : 728
VERSION : 2.0
OS : DOS
DATE : February 25, 1992 PAGE : 4/6

TITLE : Issues with Petzold's Programming Windows and Borland
C++




--- cut here ---
#
# Borland C++ makefile for Charles Petzold's Programming Windows
# examples
#
# Instructions: 1) Change "file" to the name of the example
# program being compiled.
# 2) If the example you are compiling does
# not have an RC file, remove all
# references to "file.res".
# 3) Modifications will be necessary for
# multifile examples. Consult the
# Borland C++ User's Guide.
#
file.exe : file.obj file.def file.res
bccx -W file.obj
rc file.res file.exe
# if the example does not contain an RC file, remove
# "file.res" from the line above

file.obj : file.c
bccx -W -c file.c

# if the example does not contain an RC file, remove the rule
# below
file.res :
rc -r file.rc

--- cut here ---

Note that a DEF file called file.def would be linked in
automatically. If file.def does not exist, default values would
be used.

More complex, multifile examples are most easily built using the
project manager of BCX or BC. Select "Open Project" from the
"Project" menu. Give your project a name (this will also be the
name of your executable). A project window will appear. Select
the project window and hit the "insert" key. You will be
prompted for the names of the source files to be included in your
project. Also remember to include your RC file and your DEF file
in your project. After all items are entered into your project,
select "Windows App" under the "Options | Application" menu. You












PRODUCT : Borland C++ NUMBER : 728
VERSION : 2.0
OS : DOS
DATE : February 25, 1992 PAGE : 5/6

TITLE : Issues with Petzold's Programming Windows and Borland
C++




may now compile the program by selecting "Build All" from the
"Compile" menu.

If you require or prefer to use a make file rather than the
project manager, the utility PRJ2MAK can be used to convert the
project file described above into a Borland Make-compatible make
file.

More information on Borland Make and the Project Manager can be
found in the Borland C++ User's Guide. Information on PRJ2MAK
can be found in the document UTIL.DOC which you can find in your
DOC subdirectory of Borland C++.

WARNINGS
--------
Many of the examples in Programming Windows will issue warnings
which can be ignored, such as the following:

Warning file.c 57: Parameter 'lpszCmdParam' is never used in
function WinMain(unsigned int,unsigned int,char far*,int)

The compiler correctly flags an unused parameter as a potential
problem in the code. In most programs, it would be wasteful to
define a function which is passed parameters which are never
used. However, the parameters for a Windows call back function
must all be declared so that Windows can pass messages to your
program.

This warning message can be eliminated by inserting the line:

#pragma argsused

right before the declaration of the function.

Another common warning is the following:

Warning: Attempt to export non-public symbol WndProc

This indicates that there is a function exported in your DEF file
which was not found in your program by the linker. This warning
should not be ignored since, in many cases, attempting to export
a nonexistent symbol implies that you may have missed exporting a
symbol which DOES exist. It may be that you are compiling your












PRODUCT : Borland C++ NUMBER : 728
VERSION : 2.0
OS : DOS
DATE : February 25, 1992 PAGE : 6/6

TITLE : Issues with Petzold's Programming Windows and Borland
C++




program in C++ without modifying the example (see "COMPILING IN
C++" at the top of this document).