how-programming.texinfo

cygwin, 著名的在win32下模拟unix操作系统的东东

net release.)}

Pass heap/stack linker arguments to gcc.  To create foo.exe with
a heap size of 1024 and a stack size of 4096, you would invoke
gcc as:

@code{gcc -Wl,--heap,1024,--stack,4096 -o foo foo.c}

@subsection How can I find out which dlls are needed by an executable?

@samp{objdump -p} provides this information, but is rather verbose.

@samp{cygcheck} will do this much more concisely, and operates
recursively, provided the command is in your path.

Note there is currently a bug in cygcheck in that it will not report
on a program in a Windows system dir (e.g., C:\Windows or C:\WINNT) even
if it's in your path.  To work around this, supply the full Win32 path
to the executable, including the .exe extension:

@example
cygcheck c:\\winnt\\system32\\cmd.exe
@end example

(Note the windows path separator must be escaped if this is typed in
bash.)

@subsection How do I build a DLL?

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

There's documentation that explains the process on the main Cygwin
project web page (http://cygwin.com/).

@subsection How can I set a breakpoint at MainCRTStartup?

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

Set a breakpoint at *0x401000 in gdb and then run the program in
question.

@subsection How can I build a relocatable dll?

@strong{(Please note: This section has not yet been updated for the
latest net release.  However, there was a discussion on the cygwin
mailing list recently that addresses this issue.  Read
@file{http://cygwin.com/ml/cygwin/2000-06/msg00688.html} and
related messages.)}

You must execute the following sequence of five commands, in this
order:

@example
$(LD) -s --base-file BASEFILE --dll -o DLLNAME OBJS LIBS -e ENTRY

$(DLLTOOL) --as=$(AS) --dllname DLLNAME --def DEFFILE \
        --base-file BASEFILE --output-exp EXPFILE

$(LD) -s --base-file BASEFILE EXPFILE -dll -o DLLNAME OBJS LIBS -e ENTRY

$(DLLTOOL) --as=$(AS) --dllname DLLNAME --def DEFFILE \
	--base-file BASEFILE --output-exp EXPFILE

$(LD) EXPFILE --dll -o DLLNAME OBJS LIBS -e ENTRY
@end example

In this example, $(LD) is the linker, ld.

$(DLLTOOL) is dlltool.

$(AS) is the assembler, as.

DLLNAME is the name of the DLL you want to create, e.g., tcl80.dll.

OBJS is the list of object files you want to put into the DLL.

LIBS is the list of libraries you want to link the DLL against.  For
example, you may or may not want -lcygwin.  You may want -lkernel32.
Tcl links against -lcygwin -ladvapi32 -luser32 -lgdi32 -lcomdlg32
-lkernel32.

DEFFILE is the name of your definitions file.  A simple DEFFILE would
consist of ``EXPORTS'' followed by a list of all symbols which should
be exported from the DLL.  Each symbol should be on a line by itself.
Other programs will only be able to access the listed symbols.

BASEFILE is a temporary file that is used during this five stage
process, e.g., tcl.base.

EXPFILE is another temporary file, e.g., tcl.exp.

ENTRY is the name of the function which you want to use as the entry
point.  This function should be defined using the WINAPI attribute,
and should take three arguments:
        int WINAPI startup (HINSTANCE, DWORD, LPVOID)

This means that the actual symbol name will have an appended @@12, so if
your entry point really is named @samp{startup}, the string you should
use for ENTRY in the above examples would be @samp{startup@@12}.

If your DLL calls any Cygwin API functions, the entry function will need
to initialize the Cygwin impure pointer.  You can do that by declaring
a global variable @samp{_impure_ptr}, and then initializing it in the
entry function.  Be careful not to export the global variable
@samp{_impure_ptr} from your DLL; that is, do not put it in DEFFILE.

@example
/* This is a global variable.  */
struct _reent *_impure_ptr;
extern struct _reent *__imp_reent_data;

int entry (HINSTANT hinst, DWORD reason, LPVOID reserved)
@{
  _impure_ptr = __imp_reent_data;
  /* Whatever else you want to do.  */
@}
@end example

You may put an optional `--subsystem windows' on the $(LD) lines.  The
Tcl build does this, but I admit that I no longer remember whether
this is important.  Note that if you specify a --subsytem <x> flag to ld,
the -e entry must come after the subsystem flag, since the subsystem flag
sets a different default entry point.

You may put an optional `--image-base BASEADDR' on the $(LD) lines.
This will set the default image base.  Programs using this DLL will
start up a bit faster if each DLL occupies a different portion of the
address space.  Each DLL starts at the image base, and continues for
whatever size it occupies.

Now that you've built your DLL, you may want to build a library so
that other programs can link against it.  This is not required: you
could always use the DLL via LoadLibrary.  However, if you want to be
able to link directly against the DLL, you need to create a library.
Do that like this:

$(DLLTOOL) --as=$(AS) --dllname DLLNAME --def DEFFILE --output-lib LIBFILE

$(DLLTOOL), $(AS), DLLNAME, and DEFFILE are the same as above.  Make
sure you use the same DLLNAME and DEFFILE, or things won't work right.

LIBFILE is the name of the library you want to create, e.g.,
libtcl80.a.  You can then link against that library using something
like -ltcl80 in your linker command.

@subsection How can I debug what's going on?

You can debug your application using @code{gdb}.  Make sure you
compile it with the -g flag!  If your application calls functions in
MS dlls, gdb will complain about not being able to load debug information
for them when you run your program.  This is normal since these dlls
don't contain debugging information (and even if they did, that debug
info would not be compatible with gdb).

@subsection Can I use a system trace mechanism instead?

Yes.  You can use the @code{strace.exe} utility to run other cygwin
programs with various debug and trace messages enabled.  For information
on using @code{strace}, see the Cygwin User's Guide or the file
@code{winsup/utils/utils.sgml}.

@subsection Why doesn't gdb handle signals?

Unfortunately, there is only minimal signal handling support in gdb
currently.  Signal handling only works with Windows-type signals.
SIGINT may work, SIGFPE may work, SIGSEGV definitely does.  You cannot
'stop', 'print' or 'nopass' signals like SIGUSR1 or SIGHUP to the
process being debugged.

@subsection The linker complains that it can't find something.

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

A common error is to put the library on the command line before
the thing that needs things from it.

This is wrong @code{gcc -lstdc++ hello.cc}.
This is right @code{gcc hello.cc -lstdc++}.

@subsection I use a function I know is in the API, but I still get a link error.

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

The function probably isn't declared in the header files, or
the UNICODE stuff for it isn't filled in.

@subsection Can you make DLLs that are linked against libc ?

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

Yes.

@subsection Where is malloc.h?

@strong{(Please note: This section has not yet been updated for the latest
net release.)}

Include stdlib.h instead of malloc.h.

@subsection Can I use my own malloc?

If you define a function called @code{malloc} in your own code, and link
with the DLL, the DLL @emph{will} call your @code{malloc}.  Needless to
say, you will run into serious problems if your malloc is buggy.

If you run any programs from the DOS command prompt, rather than from in
bash, the DLL will try and expand the wildcards on the command line.
This process uses @code{malloc} @emph{before} your main line is started.
If you have written your own @code{malloc} to need some initialization
to occur after @code{main} is called, then this will surely break.

Moreover, there is an outstanding issue with @code{_malloc_r} in
@code{newlib}.  This re-entrant version of @code{malloc} will be called
directly from within @code{newlib}, by-passing your custom version, and
is probably incompatible with it.  But it may not be possible to replace
@code{_malloc_r} too, because @code{cygwin1.dll} does not export it and
Cygwin does not expect your program to replace it.  This is really a
newlib issue, but we are open to suggestions on how to deal with it.

@subsection Can I mix objects compiled with msvc++ and gcc?

Yes, but only if you are combining C object files.  MSVC C++ uses a
different mangling scheme than GNU C++, so you will have difficulties
combining C++ objects.

@subsection Can I use the gdb debugger to debug programs built by VC++?

No, not for full (high level source language) debugging.
The Microsoft compilers generate a different type of debugging
symbol information, which gdb does not understand.

However, the low-level (assembly-type) symbols generated by
Microsoft compilers are coff, which gdb DOES understand.
Therefore you should at least be able to see all of your
global symbols; you just won't have any information about
data types, line numbers, local variables etc.

@subsection Where can I find info on x86 assembly?

CPU reference manuals for Intel's current chips are available in
downloadable PDF form on Intel's web site:

@file{http://developer.intel.com/design/pro/manuals/}

@subsection Shell scripts aren't running properly from my makefiles?

If your scripts are in the current directory, you must have @samp{.}
(dot) in your $PATH.  (It is not normally there by default.)  Otherwise,
you would need to add /bin/sh in front of each and every shell script
invoked in your Makefiles.

@subsection What preprocessor do I need to know about?

We use _WIN32 to signify access to the Win32 API and __CYGWIN__ for
access to the Cygwin environment provided by the dll.

We chose _WIN32 because this is what Microsoft defines in VC++ and
we thought it would be a good idea for compatibility with VC++ code
to follow their example.  We use _MFC_VER to indicate code that should
be compiled with VC++.

_WIN32 is only defined when you use either the -mno-cygwin or -mwin32
gcc command line options.  This is because Cygwin is supposed to be a
Unix emulation environment and defining _WIN32 confuses some programs
which think that they have to make special concessions for a Windows
environment which Cygwin handles automatically.

@subsection How should I port my Unix GUI to Windows?

There are two basic strategies for porting Unix GUIs to Windows.

The first is to use a portable graphics library such as tcl/tk, X11, or
V (and others?).  Typically, you will end up with a GUI on Windows that
requires some runtime support.  With tcl/tk, you'll want to include the
necessary library files and the tcl/tk DLLs.  In the case of X11, you'll
need everyone using your program to have an X11 server installed.

The second method is to rewrite your GUI using Win32 API calls (or MFC
with VC++).  If your program is written in a fairly modular fashion, you
may still want to use Cygwin if your program contains a lot of shared
(non-GUI-related) code.  That way you still gain some of the portability
advantages inherent in using Cygwin.

@subsection Why not use DJGPP ?

DJGPP is a similar idea, but for DOS instead of Win32.  DJGPP uses a
"DOS extender" to provide a more reasonable operating interface for its
applications.   The Cygwin toolset doesn't have to do this since all of
the applications are native WIN32.   Applications compiled with the
Cygwin tools can access the Win32 API functions, so you can write
programs which use the Windows GUI.

You can get more info on DJGPP by following
@file{http://www.delorie.com/}.