Bhavana –
You cannot expect MSVCRT lib to work for the UEFI application. MSVCRT expects
to make calls to low-level Windows functions.
Instead you need to link against the StdLib library class, which is a
conformant C library with fopen/fclose, etc.
Tim
From: Bhavana Brar [mailto:[email protected]]
Sent: Thursday, September 06, 2012 8:39 AM
To: [email protected]
Subject: Re: [edk2] fOpen calls within an efi application fail or hang
Thanks Daryl for responding so promptly. I'm trying to use just the standard C
library for opening files so fopen /fclose etc. I used the MSVCRT lib for this.
Why do I need to add the DevShell to the libraryClasses ?
I'm using the UDK2010 kit and I did see the ShellPkg contains File IO functions
in it. Can I not expect the standard FILE IO calls to work within the efi app
and do I specifically have to use the functions that are there in the ShellPkg?
If that is the case , why is that?
I got the file open/close to work with just the fopen/fclose ( include stdio.h).
Thanks
From: "Mcdaniel, Daryl"
<[email protected]<mailto:[email protected]>>
To:
"[email protected]<mailto:[email protected]>"
<[email protected]<mailto:[email protected]>>
Date: 09/04/2012 01:43 PM
Subject: Re: [edk2] fOpen calls within an efi application fail or hang
________________________________
Hello,
There are two possible causes for the behavior you are seeing.
1. The file system driver is not loaded. Please make sure that DevShell
is listed in the [LibraryClasses] section of your application’s .inf file.
2. The current working directory is not on the disk partition you are
attempting to access. When the Shell is first started, the current working
directory (CWD), and partition, are NULL. It is necessary to first change to
the partition you wish to access before the CWD is defined. If the Shell’s
prompt is “Shell”, then the CWD hasn’t been set. If it is something like
“fs0”, “f8” or some other name (as displayed by the map command) then the CWD
has been set.
There are, of course, an extremely large number of other possible causes;
though they are unlikely. If one of the two remedies listed above don’t take
care of the problem, I will need more detailed information.
Sincerely,
Daryl McDaniel
From: Bhavana Brar [mailto:[email protected]]
Sent: Tuesday, September 04, 2012 8:48 AM
To: [email protected]<mailto:[email protected]>
Subject: [edk2] fOpen calls within an efi application fail or hang
Hi,
I've modified the HelloWorld application to use the standard file I/O calls (
fopen_s ) to read an existing file ( "test.txt) and print out its contents.
The txt file exists in the same partition and location as the HelloWorld .efi
app ( \EFI|BOOT). I added prints before and after the fopen call and I see the
first print and then the application seems to hang.
I'm using UDK2010 ( latest version) and VS2008 .
My end goal is to be able to read/write some sort of a text file within an efi
application and then do some post processing etc.
Any ideas or suggestions on whether this should work etc?
Thanks
Bhavana
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