I would like to port PDPCLIB: http://sourceforge.net/projects/pdos/
my public domain C runtime library for DOS, OS/2,
Win32, MVS to Unix now.
I am a bit perplexed as to how to do this. Unix/Posix
systems provide open() with which I can implement
fopen(). But then Posix is also required to define fopen(),
so this is not the level at which I need to implement it.
Although I don't think the CRT should be polluting the
namespace by using open() in the first place.
If the lower level is platform-dependent, then the platform
I wish to target is Linux.
Can someone get me started?
Thanks. Paul. 21  3090 
Paul Edwards wrote:
I would like to port PDPCLIB:
http://sourceforge.net/projects/pdos/
my public domain C runtime library for DOS, OS/2,
Win32, MVS to Unix now.
I am a bit perplexed as to how to do this. Unix/Posix
systems provide open() with which I can implement
fopen(). But then Posix is also required to define fopen(),
so this is not the level at which I need to implement it.
Although I don't think the CRT should be polluting the
namespace by using open() in the first place.
If the lower level is platform-dependent, then the platform
I wish to target is Linux.
Can someone get me started?
As a system library, you'll need to only rely on the APIs exported by
the OS. Linux aims towards POSIX compliance and thus implements many
APIs defined by POSIX. The system C library often also provides POSIX
interface.
In general you should try to do as much as possible within standard C
and write specific functions when they're called for. If you want the
library to port to most UNIXes, it's structure and compilation will get
more involved. If it's specifically for Linux, then it'll be much
simpler.
At a minimum you'll need to refer to the C standard, the POSIX
standards and the man 2 pages for the OS API. The tricky part will be
satisfying the OS without sacrificing too much portability.
Post Linux API related questions to one of the Linux groups. Details
within standard C portions can be discussed here or in comp.std.c, (but
I doubt that those areas would be much of a problem for you).
The Linux newsgroups will probably help you best. Also browse the
sources of C libraries like dietlibc etc.
"santosh" <sa*********@gm ail.comwrote in message news:11******** **************@ e3g2000cwe.goog legroups.com...
Also browse the sources of C libraries like dietlibc etc.
Thanks. I found that, and their fopen() calls __libc_open()
which in turn calls __syscall_open( ).
The __syscall_open( ) is presumably what the OS exports,
and what I need to use to avoid polluting the user's namespace
by a direct call to open().
I haven't found where __syscall_open( ) is defined yet,
but I found a sys_open() in syscalls.h. Maybe that's the
proper one to use.
BFN. Paul.
Paul Edwards skrev:
[...]
I haven't found where __syscall_open( ) is defined yet,
but I found a sys_open() in syscalls.h. Maybe
that's the proper one to use.
sys_open()
sys_read()
sys_write()
sys_close()
BUT, why not look up the Linux kernel documentation or
ask in a forum where Linux is on-topic?
comp.os.linux.m isc
comp.os.linux.d evelopment.syst em
comp.os.linux.d evelopment.apps
etc.
<gd&r>
--
Tor <torust AT online DOT no>
Paul Edwards wrote On 11/17/06 15:20,:
"santosh" <sa*********@gm ail.comwrote in message news:11******** **************@ e3g2000cwe.goog legroups.com...
>>Also browse the sources of C libraries like dietlibc etc.
Thanks. I found that, and their fopen() calls __libc_open()
which in turn calls __syscall_open( ).
The __syscall_open( ) is presumably what the OS exports,
and what I need to use to avoid polluting the user's namespace
by a direct call to open().
I haven't found where __syscall_open( ) is defined yet,
but I found a sys_open() in syscalls.h. Maybe that's the
proper one to use.
Why is it better to pollute the user's namespace
with sys_open() than with open()?
-- Er*********@sun .com
Paul Edwards wrote:
"santosh" <sa*********@gm ail.comwrote in message news:11******** **************@ e3g2000cwe.goog legroups.com...
Also browse the sources of C libraries like dietlibc etc.
Thanks. I found that, and their fopen() calls __libc_open()
which in turn calls __syscall_open( ).
The __syscall_open( ) is presumably what the OS exports,
and what I need to use to avoid polluting the user's namespace
by a direct call to open().
I haven't found where __syscall_open( ) is defined yet,
but I found a sys_open() in syscalls.h. Maybe that's the
proper one to use.
No. This is still a feature of the existing C library. If you want your
CRT to be independant of other libraries, you must directly call the
kernel by means of assembler, (either INT, SYSCALL, SYSENTER etc). The
API exported by the kernel is available in the 'asm/unistd.h' header
for UNIX like kernels. For each defined syscall, refer to it's man 2
page for the official documentation, but they're often not good enough
to enable you to write robust code, (especially for newer system
calls). As the ultimate reference, the kernel's source may have to
consulted.
To enable the rest of your library to be portable, you'll probably want
to create wrappers around system calls, just like existing sys_open()
sys_write() etc.
"Eric Sosman" <Er*********@su n.comwrote in message news:1163805399 .935710@news1nw k...
The __syscall_open( ) is presumably what the OS exports,
and what I need to use to avoid polluting the user's namespace
by a direct call to open().
I haven't found where __syscall_open( ) is defined yet,
but I found a sys_open() in syscalls.h. Maybe that's the
proper one to use.
Why is it better to pollute the user's namespace
with sys_open() than with open()?
Technically it isn't, but since no-one actually uses sys_open(),
I didn't think anyone would notice.
I have the same problem with Win32. It is polluting the user's
namespace with CreateFile(). I don't know how to get around
that. I wonder what other C compilers do?
BFN. Paul.
Paul Edwards said:
"Eric Sosman" <Er*********@su n.comwrote in message
news:1163805399 .935710@news1nw k...
>>
Why is it better to pollute the user's namespace
with sys_open() than with open()?
Technically it isn't, but since no-one actually uses sys_open(),
I didn't think anyone would notice.
I have the same problem with Win32. It is polluting the user's
namespace with CreateFile(). I don't know how to get around
that. I wonder what other C compilers do?
Don't worry about it. Since no-one actually uses CreateFile() - except as a
Win32 API call - I don't think anyone will notice.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999 http://www.cpax.org.uk
email: normal service will be restored as soon as possible. Please do not
adjust your email clients.
Eric Sosman skrev:
Paul Edwards wrote On 11/17/06 15:20,:
[...]
The __syscall_open( ) is presumably what the OS exports,
and what I need to use to avoid polluting the user's namespace
by a direct call to open().
Why is it better to pollute the user's namespace
with sys_open() than with open()?
I don't get it. Why does the standard library pollute user's
namespace?
Internally, the library will have e.g. <open.c>, which calls the
OS functions. So those OS calls shouldn't be visable to the
library caller... so is it a link problem we talk about here?
--
Tor <torust AT online DOT no>
"Tor Rustad" <to********@hot mail.comwrote in message news:11******** *************@m 73g2000cwd.goog legroups.com...
Eric Sosman skrev:
Paul Edwards wrote On 11/17/06 15:20,:
[...]
The __syscall_open( ) is presumably what the OS exports,
and what I need to use to avoid polluting the user's namespace
by a direct call to open().
Why is it better to pollute the user's namespace
with sys_open() than with open()?
I don't get it. Why does the standard library pollute user's
namespace?
Internally, the library will have e.g. <open.c>, which calls the
OS functions. So those OS calls shouldn't be visable to the
library caller... so is it a link problem we talk about here?
Yes, the problem will occur at link time. The C library is
not meant to be dependent on functions which are in the
user's namespace. The C library is allowed to use names
such as __open() or _Open() (on a case-sensitive system),
but not open().
BFN. Paul. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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