Can somebody explain these lines in this code?

Question

In this source-code of Arwin I saw :

fprc_func = GetProcAddress(hmod_libname,argv[2]);

if(fprc_func == NULL)
{
    printf("Error: could find the function in the library!\n");
    exit(-1);
}
printf("%s is located at 0x%08x in %s\n",argv[2],(unsigned int)fprc_func,argv[1]);

Why we use exit(-1) and not use exit(1) here ?

Also please explain the printf statement in a understanding way.

Having a different error code? Any non-zero value means failure, so -1 is a choose for an exit code (wrapper around, most likely 127) — JVApen, Apr 23 '16 at 12:53

sjsam · Accepted Answer · 2016-04-23T13:05:03.877

2

Whether to use exit(-1) or exit(1) for failure is a personal choice.

POSIX compliant code uses 1 or EXIT_FAILURE for failures

In

printf("%s is located at 0x%08x in %s\n",argv[2],(unsigned int)fprc_func,argv[1]);

Two strings argv[2] & argv[1] (as specified by %s) and an unsigned hexadecimal integer fprc_func (as specified by 0x%08x) are printed. The %08 in 0x%08x is for setting the width to eight. See printf doc.

edited Apr 23 '16 at 13:05

answered Apr 23 '16 at 12:54

sjsam

21,411
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@piratos - I have done an edit to the question. You may approve it – sjsam Apr 23 '16 at 13:41

score 0 · Answer 2 · answered Apr 23 '16 at 13:03

0

printf("%s is located at 0x%08x in %s\n",argv[2],(unsigned int)fprc_func,argv[1]);

The first %s refers to the argv[2].

The %08x refers to fprc_func in hex with 8 zeroes, where fprc_func is a function pointer returned by GetProcAddress. The (unsigned int) cast the address to unsigned integer (never negative).

The last %s refers to argv[1].

More info about printf format can be found here: http://www.cplusplus.com/reference/cstdio/printf/

answered Apr 23 '16 at 13:03

raymai97

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Let me add an example: assuming you use `%03i`, if the int is 12, it will show 012, if the int is 3, it will show 003. – raymai97 Apr 23 '16 at 13:17

Can somebody explain these lines in this code?

2 Answers2