Mail Archives: cygwin/1998/10/29/12:24:47
gcc is a real C compiler when it compiles C, C allows you to use
undeclared functions, assuming that all undeclared functions are
"extern int". Since a to f returns a double, not a float, I would
assume that there is a call setup/teardown problem that occurs due
to the incorrect assumption about the return type of the function.
To quote from K&R 2nd edition, page 72:
"...But if (as is more likely) atof were compiled seperately, the
mismatch would not be detected atof() would return a double that
main() would treat as an int, and meaningless answers would result."
None of this is a "bug" except in your code.
-Peter
Peter A. Vogel
Manager, SW Configuration Management
Chromatic Research, Inc.
http://www.chromatic.com
> -----Original Message-----
> From: owner-gnu-win32 AT cygnus DOT com [mailto:owner-gnu-win32 AT cygnus DOT com]On
> Behalf Of Martin Hansen
> Sent: Tuesday, October 27, 1998 4:11 AM
> To: gnu-win32 AT cygnus DOT com
> Subject: B19: gcc/libc bug with call to atof() (Win95)
>
>
> Dear list,
>
> in my version of gnu-win32 I encounter the following bug with
> gcc/libc.
> I have the gnu-win32 version B19 running under Win95 (4.00.950 B).
> Within the gnu-win32 distribution I have the gcc version
> % gcc -v
> Reading specs from
> C:\CYGNUS\B19\H-I386~1\lib\gcc-lib\i386-cygwin32\2.7-B19\specs
> gcc driver version 2.7-B19 executing gcc version 2.7-97r2aBeta
>
>
>
> The following small program produces the bug:
>
> /* test_atof.c */
>
> #include <stdio.h>
>
> main(int argc, char **argv)
> {
> while (--argc)
> {
> printf("\narg %d is %s\n", argc, argv[argc]);
> printf("arg %d : value as float %f\n", argc, atof(argv[argc]));
> printf("arg %d : value as int %d\n", argc, atoi(argv[argc]));
> }
> }
>
> /* End of file */
>
>
>
>
> Compile the program by
> % gcc test_atof.c
> The program compiles and I don't get any error about the missing line
> "#include <stdlib.h>", where atoi() and atof() are declared. (This is
> the bug, part1)
>
> Try the program with
> % test_atof 3.3 4.7
> The result is
>
> arg 2 is 4.7
> arg 2 : value as float 0.000000
> arg 2 : value as int 4
>
> arg 1 is 3.3
> arg 1 : value as float 0.000000
> arg 1 : value as int 3
>
> which is wrong for the float value but right for the int value. (This
> is the bug, part2). First when you add the line '#include <stdlib.h>'
> to the program and recompile it, you get the desired behaviour.
> -
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