How to determine your machine is “Little Endian” or “Big Endian”.

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What is big and Little Endian ?

Little and big endian are two ways of storing multibyte data-types ( int, float, etc). In little endian machines, last byte of binary representation of the multibyte data-type is stored first. On the other hand, in big endian machines, first byte of binary representation of the multibyte data-type is stored first.

Big Endian(Wikipedia)

Little Endian(Wikipedia)

Is there a quick way to determine endianness of your machine?
There are n no. of ways for determining endianness of your machine. Here is one quick way of doing the same.

#include <stdio.h>

int main()

{

unsigned int i = 1;

char *c = (char*)&i;

if (*c)

printf("Little endian");

else

printf("Big endian");

getchar();

return 0;

}

In the above program, a character pointer c is pointing to an integer i. Since size of character is 1 byte when the character pointer is de-referenced it will contain only first byte of integer. If machine is little endian then *c will be 1 (because last byte is stored first) and if machine is big endian then *c will be 0.

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How to get a “codesigned” gdb on OS X?

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Very interesting problem, I wanted to run gdb on my mac but i was not able to to run it. Because it was not codeSigned . Here’s the solution.

The Darwin Kernel requires the debugger to have special permissions before it is allowed to control other processes. These permissions are granted by codesigning the GDB executable. Without these permissions, the debugger will report error messages such as:

Starting program: /x/y/foo
Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5).
 (please check gdb is codesigned - see taskgated(8))

Codesigning requires a certificate. The following procedure explains how to create one:

(Note ) : I tried many times creating certificate for gdb, basic problem was while creating certificate, Please Create certificate for “System” not for “login” that is main problem.

Start the Keychain Access application (in /Applications/Utilities/Keychain Access.app)
Select the Keychain Access -> Certificate Assistant -> Create a Certificate… menu
Then:
- Choose a name for the new certificate (this procedure will use “gdb-cert” as an example)
- Set “Identity Type” to “Self Signed Root”
- Set “Certificate Type” to “Code Signing”
- Activate the “Let me override defaults” option
Click several times on “Continue” until the “Specify a Location For The Certificate” screen appears, then set “Keychain” to “System”
Click on “Continue” until the certificate is created
Finally, in the view, double-click on the new certificate, and set “When using this certificate” to “Always Trust”
Exit the Keychain Access application and restart the computer (this is unfortunately required)

Once a certificate has been created, the debugger can be codesigned as follow. In a Terminal, run the following command…

codesign -f -s  "gdb-cert"  <gnat_install_prefix>/bin/gdb

… where “gdb-cert” should be replaced by the actual certificate name chosen above, and should be replaced by the location where you installed GNAT.

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