489 lines
22 KiB
Plaintext
489 lines
22 KiB
Plaintext
**********************************************************
|
|
* Corrections to the Power C manual and New Features *
|
|
**********************************************************
|
|
|
|
Some instructions in the Getting Started section of the Power C manual
|
|
are now incorrect.
|
|
|
|
In the Arranging Files on a Hard Disk sub-section, you should ignore the
|
|
MD and COPY commands since the INSTALL program takes care of making the
|
|
directories and copying the files. However, you should execute the
|
|
MD MYFILES command on page 6 to create a directory for storing your own
|
|
programs, since the INSTALL program does not create the MYFILES directory.
|
|
|
|
In the Arranging Files on Floppies sub-section, if you have 5 1/4"
|
|
drives, you should substitute disk 3 of 4 where it mentions copying
|
|
the sample programs from disk 2 of 2 on page 7. The disk 2 of 2 is
|
|
correct if you are using 3 1/2" diskettes.
|
|
|
|
In the remaining sub-sections of the Getting Started section, if you
|
|
have 5 1/4" diskettes, disk 1 of 2 is now disk 1 of 4 and disk 2 of 2
|
|
is now disk 2 of 4. If you have 3 1/2" diskettes, you should substitute
|
|
disk 1 of 2 everywhere disk 2 of 2 appears since the INSTALL program
|
|
copies both the compiler and the linker onto the same diskette.
|
|
|
|
|
|
NEW FEATURES IN VERSION 2.0
|
|
|
|
Memory models:
|
|
Memory models are a reflection of the addressing modes of the
|
|
8086 family of processors. The 8086 family uses 64k segments.
|
|
Special techniques are required to exceed the 64k limits on code
|
|
and data. A simple (16 bit) address is confined to one 64k
|
|
segment. These are called "near" addresses. It is also
|
|
possible to use an address that occupies 32 bits. These "far"
|
|
addresses are normally stored as a segment number and a
|
|
corresponding offset.
|
|
|
|
In small memory model, the code resides in a single 64k or
|
|
smaller segment. Calls to functions use "near" addresses.
|
|
The data in small model is also located in a single 64k or
|
|
smaller segment. Data references also use "near" pointers.
|
|
The advantage of small memory model is that the code is
|
|
smaller than the other models since function calls use 3
|
|
bytes instead of 5 bytes.
|
|
|
|
In medium memory model, the code can occupy more than 64k of
|
|
memory. All function calls use "far" addresses. In Power C,
|
|
each function starts a new segment. This allows any function to
|
|
be up to 65520 bytes in length. The data in medium model is
|
|
located in a single 64k or smaller segment. Data references use
|
|
"near" pointers. Medium model is usually the best choice for
|
|
most programs. Code size is not limited and any large blocks of
|
|
data can be declared as far if 64k of data is not enough.
|
|
|
|
Large memory model uses unlimited code space like medium memory
|
|
model. Data in large memory model can occupy more than 64k of
|
|
memory. References to data in large model are with "far"
|
|
pointers. Large model is the least efficient of the memory
|
|
models. Each reference to a pointer takes more time and
|
|
generates more code. Large model is a good choice for programs
|
|
originally developed for larger computers that do not use
|
|
segmentation.
|
|
|
|
Large memory model
|
|
Large memory model is selected with the /ml compiler switch.
|
|
In large memory model, all pointers are far by default. You
|
|
can still use near pointers by including the "near" keyword.
|
|
Near pointers can only point to objects that are "near" or
|
|
auto.
|
|
|
|
Global variables may be near or far depending on their size.
|
|
Small variables (less than 256 bytes) are stored in near
|
|
memory by default. This allows them to be accessed more
|
|
quickly. Larger variables are stored in far memory. You
|
|
can always override the storage class with the "near" or
|
|
"far" keyword. Also, you can change the default size for
|
|
far variables with the /z compiler switch.
|
|
|
|
Addressing is done using near addresses whenever the variable
|
|
is auto or is in near memory. If a pointer or address is
|
|
passed to a function, it is automatically converted to a far
|
|
pointer.
|
|
|
|
Small memory model
|
|
|
|
Small memory model is selected with the /ms compiler switch.
|
|
In small memory model you are limited to 64k of code. Small
|
|
model is a good choice for programs that do not need more than
|
|
64k. The program will be smaller and slightly faster in small
|
|
model.
|
|
|
|
Far and huge data
|
|
|
|
Far and huge data is supported by Power C in all memory models.
|
|
You can declare a variable to be far or huge by including the
|
|
far or huge keyword in the declaration. To specify the storage
|
|
for a variable, the keyword should be immediately before the
|
|
variable name. Examples:
|
|
|
|
char far a[200]; /* far array of 200 characters */
|
|
char * far b[200]; /* far array of 200 pointers to char */
|
|
char far * far c[200]; /* far array of 200 far pointers */
|
|
char far *d[10]; /* near array of 10 far pointers */
|
|
int huge e[40000]; /* huge array of 40000 integers */
|
|
|
|
Huge arrays and structures can be as large as available memory will
|
|
allow. Huge variables can be larger than 64k bytes. Since
|
|
addressing a huge array or structure requires calculating both
|
|
a segment value and an offset, access to huge objects is slower
|
|
than access to far objects. You should use huge variables and
|
|
huge pointers only when you need the ablity to have an object
|
|
larger than 64k.
|
|
|
|
New pragma:
|
|
#pragma library "libname"
|
|
Allows you to specify a library to be searched when the
|
|
program is linked. The library name can contain '?' or
|
|
'*' to specify memory models. Any '?' character will be
|
|
replaced with the letter: 'S', 'M' or 'L' depending on
|
|
the memory model. A '*' character will be replaced by
|
|
'L' for large model 'S' for small model, and deleted for
|
|
medium model. This option is especially useful in headers.
|
|
For example, the header for a database library can include
|
|
the library name for linking.
|
|
|
|
#pragma library "\\c\\db\\isam*.lib"
|
|
#pragma library "\\c\\db\\cbt*.lib"
|
|
|
|
|
|
New warnings:
|
|
226 Array is too small to store terminating '\0' character
|
|
An array was declared with a specific size and then
|
|
initialized with a string literal. The size of the array
|
|
is equal to the size of the string without the '\0' terminator.
|
|
This array should not be used with string functions such as
|
|
strlen(). Example:
|
|
|
|
char a[3] = "abc";
|
|
|
|
227 Syntax error in #pragma
|
|
A pragma was specified but did not have the correct arguments.
|
|
For example, #pragma library requires the name of a library
|
|
as a string.
|
|
|
|
228 Function exit without a return value
|
|
The function returns a value (is not void) but does not
|
|
contain a return statement at the end.
|
|
|
|
229 Type conversion may cause overflow
|
|
An assignment or passing an argument to a function causes
|
|
a conversion of a larger type to a smaller one (such as
|
|
int to char). This conversion may lose information since
|
|
the smaller type cannot represent all possible values of
|
|
the larger. If you know that the conversion will not
|
|
overflow, you should use a type cast to perform it.
|
|
|
|
230 Item has the same name as a macro
|
|
231 Macro name already used for a variable or type
|
|
This warning indicates that a macro has the same name as a
|
|
variable or function. Although this is legal, it can be a
|
|
source of confusion.
|
|
|
|
232 Assignment of double to float may cause overflow
|
|
An expression of type double is assigned to a variable of
|
|
type float. This may result in an overflow or loss of
|
|
precision. This warning is only enabled if warning 229 is
|
|
also enabled. The /w switch (with no arguments) does not
|
|
turn on this warning. To enable it, you should use /w+232.
|
|
|
|
New compiler switches:
|
|
/ms, /ml specify small or large memory model
|
|
/z gives the threshold size for far variables in large
|
|
memory model. Global variables less than or equal to
|
|
this size are placed in near memory, and larger variables
|
|
are placed in far memory. The /z may be followed by a
|
|
size as a decimal number. A size of zero, makes all global
|
|
variables far unless they have a near keyword. /z is
|
|
equivalent to /z0. The default threshold size is 256 bytes.
|
|
|
|
/a Adjust variable addresses to word or double word boundaries.
|
|
/a or /aw places all 2 byte or larger variables at an even
|
|
address. /ad places all 4 byte or larger variables at an
|
|
address that is a multiple of 4, and all 2 byte variables
|
|
at an even address. This option will improve speed on
|
|
computers with a 16 bit or wider memory bus (such as the
|
|
IBM AT or other 80286 base machines).
|
|
|
|
Predefined macros
|
|
|
|
__POWERC - value is the version of power C. Versions less than 1.2
|
|
have the value "1". Version 1.2 is "120", 1.3.0 is "130"
|
|
and version 2.0.0 is "200".
|
|
|
|
M_I86SM - defined if small memory model
|
|
M_I86MM - defined if medium memory model
|
|
M_I86LM - defined if large memory model
|
|
__LINE__ - current compiler line number
|
|
__FILE__ - name of source file
|
|
__DATE__ - compile date
|
|
__TIME__ - compile time
|
|
__STDC__ - standard C, "1" if extended keywords are disabled,
|
|
"0" if extended keywords are enabled.
|
|
|
|
New library functions
|
|
|
|
void getimage(int left, int top, int right, int bottom,
|
|
void far *buffer);
|
|
|
|
Stores a bit image of a section of the graphics screen in a
|
|
buffer. The image can then be placed anywhere on the screen
|
|
using putimage(). The coordinates of the upper left (left,top)
|
|
and lower right (right,bottom) corners determine the area saved.
|
|
The size of buffer needed can be determined by calling imagesize().
|
|
|
|
void putimage(int left, int top, void far *buffer, int operation);
|
|
|
|
Copies a bit image to the screen. The image must have been
|
|
previously saved with getimage(). The image is placed on the
|
|
screen with its upper left corner at the coordinate given by
|
|
(left,top). The size of the image was stored as the first two
|
|
words of the buffer by getimage(). When the image is placed
|
|
on the screen, each pixel of the image can be combined with the
|
|
previous screen contents as specified by the operation. The
|
|
operations are:
|
|
|
|
COPY_PUT 0 copy the image over the previous contents
|
|
XOR_PUT 1 exclusive or with the previous contents
|
|
OR_PUT 2 inclusive or with the previous contents
|
|
AND_PUT 3 logical and with the previous contents
|
|
NOT_PUT 4 copy the inverse of each image pixel
|
|
|
|
long imagesize(int left, int top, int right, int bottom);
|
|
|
|
Returns the size of the buffer needed to store an image.
|
|
|
|
Setting the background color for plots and plotch:
|
|
The background of characters is controlled by the variable _v_bkgd.
|
|
It can be declared as:
|
|
|
|
extern int near _v_bkgd;
|
|
|
|
Setting _v_bkgd to a color sets the background color for characters.
|
|
Setting _v_bkgd to TRANSPARENT causes the background to be unchanged
|
|
and the previous contents of the screen to show in areas behind the
|
|
character.
|
|
|
|
Graphics using the bios:
|
|
For extended video modes and machines where the graphics do not match
|
|
the IBM PC memory mapping, you can force all graphics routines to use
|
|
the BIOS. To do this, set the variable _vusemem to 0. Example:
|
|
|
|
extern int near _vusemem;
|
|
_vusemem = 0;
|
|
|
|
|
|
Mix.exe
|
|
|
|
The conversion utility now has a switch to eliminate extra underscore
|
|
("_") characters from the beginning of external names. Some compilers
|
|
generate an extra leading underscore character on all external names.
|
|
If you are converting an assembly function originally written for
|
|
one of these compilers, you can use the "/_" switch to eliminate the
|
|
extra underscore.
|
|
|
|
|
|
New Features in version 1.3
|
|
|
|
Power C now supports pre-compiled headers. Much of the time in
|
|
compiling a C program is spent compiling the standard headers that the
|
|
program includes to declare standard functions. Power C will allow the
|
|
headers to be pre-compiled into a header library. The pre-compiled
|
|
headers are much faster than compiling the source for the headers.
|
|
|
|
By default, the compiler will search for a header library named
|
|
headers.hhh. A library by this name containing the standard headers
|
|
is supplied on your release disk. The header library can be found
|
|
in the default directory or any directory that would normally be
|
|
searched for headers. You can also specify a header library on the
|
|
command line by including the switch "/h" or "-h" followed by the
|
|
name of the library. An option of "/h" or "/h-" will disable the
|
|
header library feature.
|
|
|
|
Header libraries and pre-compiled header files are created and
|
|
maintained by the program "fasthdr.exe" supplied on your release
|
|
disk. This program can add, delete or replace headers in a library.
|
|
It can also create individual pre-compiled header files. The
|
|
default is to create a header library named "headers.hhh" in the
|
|
current default directory. The command line can contain a list of
|
|
headers (including wild cards). For example:
|
|
|
|
fasthdr a:*.h a:sys\*.h
|
|
|
|
If the disk in drive A contains the Power C release disk 1, the above
|
|
command will create a header library file named headers.hhh in the current
|
|
directory. The headers.hhh file will contain all of the standard
|
|
header files. If the header.hhh file already exists, the above command
|
|
would simply add the specified headers to the library and replace any
|
|
previously stored headers having the same name.
|
|
|
|
The /d switch is used to delete headers from the library. You can
|
|
give a list of headers to delete. Wild cards are not supported. For
|
|
example, the following command will delete time.h and math.h from the
|
|
library.
|
|
|
|
fasthdr /d time.h math.h
|
|
|
|
The /o switch allows you to specify a file or directory in which
|
|
the compiled headers will be stored. If the /o is followed by a file
|
|
name (with or without a directory prefix), then the headers are compiled
|
|
and stored in the specified library file. If the /o is followed by a
|
|
directory name only, then rather than create a single library file,
|
|
the fasthdr program creates a separate compiled header file for each
|
|
header file specified on the command-line and stores them in the specified
|
|
directory. In this case, the compiled header files will have the same
|
|
name as the original header files, so the directory specified for the
|
|
compiled header files should not be the same as the directory containing
|
|
the original header files.
|
|
|
|
The /f switch specifies that you want each header converted to
|
|
a separate file. The pre-compiled header will have the same name
|
|
as the original header and the original header will be renamed with
|
|
the extension ".hxt". Use /f switch rather than the /o switch if
|
|
you want the compiled header files to be stored in the same directory
|
|
with the original header files.
|
|
|
|
The /l switch gives a listing of the headers in a library.
|
|
|
|
--------
|
|
|
|
Power C (versions 1.2 and later) generate names up to 31 characters in
|
|
length for use by Power Ctrace version 1.2. Use of names longer than 8
|
|
characters requires version 1.2 or later of Power Ctrace. If you have an
|
|
earlier version of Power Ctrace, you must use the new /t8 compile option
|
|
rather than the /t option for debugging.
|
|
|
|
--------
|
|
|
|
Compiler error messages are now displayed differently than
|
|
described in the Power C manual. The example compile error described
|
|
on page 625 will now be displayed as follows. Notice that the
|
|
file name test.C precedes the line number rather than being displayed
|
|
on a separate line.
|
|
|
|
test.C(1):main() {printf("hello world\n")}
|
|
********* ^ 14
|
|
14: ';' expected
|
|
|
|
--------
|
|
|
|
Some warning messages have been added to the compiler. The warnings
|
|
are displayed to indicate that something is dangerous and possibly
|
|
incorrect but not strictly illegal. When warnings are issued, the
|
|
compiler generates the correct code for the source as written.
|
|
In many cases warnings can be disabled or ignored.
|
|
|
|
Warnings are disabled by default. Warning messages are enabled
|
|
with the "/w" or "-w" switch on the command line. Use /w to enable
|
|
all of the warnings or /w- to disable them. Individual
|
|
warnings can be turned on (or off) with /w+n (or /w-n) where n is
|
|
the warning number. For example "/w+221" causes the compiler to check
|
|
the types of pointers. In this case, a message will be diplayed if a
|
|
pointer to int is assigned to a pointer to char (unless a cast is present).
|
|
|
|
Warnings can also be controlled within the source file with
|
|
#pragma warning. Examples:
|
|
|
|
#pragma warning /* enable all warnings */
|
|
#pragma warning -224 /* don't report unused variables */
|
|
#pragma warning 221 /* check pointer types */
|
|
|
|
The warnings are:
|
|
|
|
220 - unknown pragma
|
|
221 - assignment or argument passing with pointers of different types
|
|
222 - assignment or argument passing with a pointer when a scalar
|
|
(int, unsigned ... etc) is expected, or use of a scaler when
|
|
a pointer is expected. (use a cast to override)
|
|
223 - A variable was defined but not used in the function
|
|
224 - Call to an undeclared function. The compiler assumes that
|
|
the function is of type int.
|
|
225 - #undef was used to undefine a symbol that is not a macro
|
|
|
|
--------
|
|
|
|
An additional preprocessor directive has been added:
|
|
|
|
#error message
|
|
causes the compiler to issue an error message
|
|
and stop the compilation
|
|
|
|
--------
|
|
|
|
Corrections to the manual:
|
|
|
|
Page 344: farmalloc does NOT initialize the allocated memory
|
|
to 0. Use farcalloc if you want the memory initialized.
|
|
|
|
Page 367: _fmalloc does NOT initialize the allocated memory to 0.
|
|
Note that _fmalloc allocates first from the far heap. If
|
|
the far heap is used up, _fmalloc will allocate from the
|
|
near heap. Because of this you must use _ffree to release
|
|
memory allocated with _fmalloc. Do NOT use farfree for
|
|
this purpose as it requires that the memory be from the
|
|
far heap.
|
|
|
|
--------
|
|
|
|
Additions to the manual:
|
|
=======================
|
|
|
|
|
|
The MERGE Program
|
|
_________________
|
|
|
|
|
|
The MERGE program is used to create a single library file from
|
|
several object files. It can also be used to add new functions to
|
|
an existing library or replace existing functions with new
|
|
versions.
|
|
|
|
Usage: merge libraryfile updatefile1 updatefile2 ...
|
|
or merge libraryfile @controlfile
|
|
|
|
MERGE accepts the name of a library followed by the names of one
|
|
or more update files. The names must be separated by commas or
|
|
blanks. The default extension for all file names is MIX. If the
|
|
library file (ie. first file name) does not exist, it will be
|
|
created. All of the functions in the list of update files are
|
|
added to the library. If any function already exists in the
|
|
library, it is replaced by the new copy.
|
|
|
|
If the list of update files is too long to specify on the
|
|
command-line, you may specify the name of a control file.
|
|
The name of the control file must be prefixed by the @ symbol.
|
|
The control file may contain one or more lines of update file
|
|
names separated by blanks or commas.
|
|
|
|
When an existing library file is updated with new functions,
|
|
the new functions will appear at the beginning of the
|
|
library file. This can cause the library file to be searched
|
|
more than once if other functions appearing later in the
|
|
library reference one or more of the new functions that appear
|
|
at the beginning of the library. To control the order of
|
|
functions in the standard libraries so that they can always
|
|
be searched in one pass, the batch files delete the old copy
|
|
of the library before creating a new one.
|
|
|
|
Note: When the MERGE program is executed, there must be
|
|
enough free disk space to temporarily store two
|
|
copies of the library file.
|
|
|
|
By default, the MERGE program creates a library in a compressed
|
|
format that is smaller than a standard object file as created
|
|
by the compiler. These compressed libraries can be searched
|
|
much faster than an object file. If you wish to create a library
|
|
that is compatable with versions of Power C earlier than 1.2,
|
|
you should use the -1 switch when you execute merge.
|
|
|
|
--------
|
|
|
|
The linker (PCL.EXE) recognizes an additional environment variable.
|
|
The variable LIBNAMES specifies a list of libraries that you want
|
|
searched in addition to the standard libraries. Multiple library
|
|
names must be separated by a semicolons. Libraries specified by
|
|
the LIBNAMES environment variable are searched after the libraries
|
|
specified on the command line and before the standard libraries. For
|
|
example, if you are linking a set of programs that need functions from
|
|
a windows library:
|
|
set libnames=windows
|
|
pcl program
|
|
|
|
is equivalent to:
|
|
|
|
pcl program;windows
|
|
|
|
The libraries specified by LIBNAMES may contain drive and/or
|
|
directory prefixes. A prefix is not required if the library
|
|
is in one of the directories specified by either the LIBRARY
|
|
or PATH environment variable.
|
|
|
|
The linker has an additional command line option. The /c option
|
|
causes the linker to ignore case in all function and variable
|
|
names. Use of this switch is discouraged, but it can be useful
|
|
when linking with functions written in assembly language. The
|
|
default in MASM is to convert all external names to upper case.
|
|
A better solution is to assemble with the /Ml MASM switch.
|
|
|
|
--- end of file ---
|