// ******************************************************************
//
// bugreport.c
//
// This short little program demonstrates what I believe to be a bug
// in the otherwise-amazing GMP library.
//
// Details:
// 1. mpz_out_raw() is used to dump 4 values to a file.
// 
// 2. When the program is run again, we attempt to read
//    in the previously saved values using mpz_inp_raw().
//    The 4 saved values are loaded correctly, but an extra
//    unexpected value is also loaded.
// 
// Command Used to Compile:
// 	gcc -lgmp -o bugreport bugreport.c
//
// Usage instructions:
// 1.  Compile using the above line.
// 2.  Run the program once.
// 3.  Run the program again and note extra loaded value.
//
// Tested on the following configurations:
//
// 1.  AMD Athlon (Classic, the old Slot-A beasts), 
// 		default Linux Mandrake 8.2 install
// 		`gcc -v` yields:
// 		
// 		Reading specs from /usr/lib/gcc-lib/i586-mandrake-linux-gnu/2.96/specs
// 		gcc version 2.96 20000731 (Mandrake Linux 8.2 2.96-0.76mdk)
//
// 		GMP installed from RPM: `rpm -qi libgmp3 | grep -i version` yields:
// 			Version     : 3.1.1
//
// 2.  Intel Celeron (Laptop), default Linux Mandrake 8.2 install
// 		'gcc -v' is the same as above
//
// 		GMP version 4.1 was compiled/installed from source
// 
// 
// Keep up the great work!
// Peter Kristolaitis
// address@hidden
// 
// ******************************************************************

#include <stdio.h>
#include <gmp.h>

int main() {
	FILE *fd;
	
	// try to open the file in read mode to see if it exists...
	fd = fopen("numbers.lst", "r");

	if ( fd == NULL ) {
		// file DOESN'T exist... open the file for writing and
		// dump some values to it	
		printf("File doesn\'t exist... creating it!\n");
		fd = fopen("numbers.lst", "w");
		
		if ( fd != NULL ) {
			// file opened for writing... dump 4 values to it
			// ( use the first four prime numbers, just for fun )
			mpz_t bigNum;

			printf("Saving value of 2...\n");
			mpz_init ( bigNum );
			mpz_add_ui ( bigNum, bigNum, 2 );
			mpz_out_raw ( fd, bigNum );
			mpz_clear ( bigNum );
			
			printf("Saving value of 3...\n");
			mpz_init ( bigNum );
			mpz_add_ui ( bigNum, bigNum, 3 );
			mpz_out_raw ( fd, bigNum );
			mpz_clear ( bigNum );
			
			printf("Saving value of 5...\n");
			mpz_init ( bigNum );
			mpz_add_ui ( bigNum, bigNum, 5 );
			mpz_out_raw ( fd, bigNum );
			mpz_clear ( bigNum );

			printf("Saving value of 7...\n");
			mpz_init ( bigNum );
			mpz_add_ui ( bigNum, bigNum, 7 );
			mpz_out_raw ( fd, bigNum );
			mpz_clear ( bigNum );

			printf("Closing file...\n");
			fclose(fd);
			
			printf("All done!\n");
			printf("Saved 4 values to file.\n");
			printf("Run this program again to see the bug!\n");

		} else {
			printf("Couldn\'t open file for writing!\n");
			return 1;
		}
		
	} else {
		// file already exists... load values from file...
		// Note that file is already open for reading!
		mpz_t bigNum;
		unsigned count = 0;
		
		printf("File already exists... loading values from file.\n");
		
		mpz_init ( bigNum );
		
		while ( !feof(fd) ) {
			mpz_inp_raw ( bigNum, fd );
			printf("Loaded value ");
			mpz_out_str ( stdout, 10, bigNum );
			printf(" from file.\n");
			count++;
		}

		printf("Loaded %d values from file.\n", count);
		fclose(fd);
	}

	return 0;
}