On 07/18/2017 06:33 PM, Jonathan Wakely wrote:
On 18 July 2017 at 21:46, Dennis Clarke wrote:
Fascinating. I never would have thought that a zero line length file
would be accepted as valid. However gcc ( older rev 4.9.2 ) will
accept this :
$ printf "int main ( int argc, char* argv[] ) { return 0; }" > tzero.c
Aside: why would you bother to declare parameters for such a program?
What's wrong with int main(void) ?
I wonder about this every time somebody reports a bug that gives
-Wunused-parameter warnings because of pointless unused parameters.
Since C99 (and in C++) you don't even need the return statement.
int main() { }
Just for giggles let's use the argc parameter :
0000000 69 6e 74 20 6d 61 69 6e 20 28 20 69 6e 74 20 61
i n t m a i n ( i n t a
0000010 72 67 63 2c 20 63 68 61 72 2a 20 61 72 67 76 5b
r g c , c h a r * a r g v [
0000020 5d 20 29 20 7b 20 72 65 74 75 72 6e 20 61 72 67
] ) { r e t u r n a r g
0000030 63 3b 20 7d
c ; }
------------------ output assembly ----------------------
1 .file "tzero.c"
2 .section ".text"
3 .align 4
4 .global main
5 .type main, #function
6 .proc 04
7 main:
8 save %sp, -176, %sp
9 mov %i0, %g1
10 stx %i1, [%fp+2183]
11 st %g1, [%fp+2175]
12 ld [%fp+2175], %g1
13 sra %g1, 0, %g1
14 mov %g1, %i0
15 return %i7+8
16 nop
17 .size main, .-main
18 .ident "GCC: (genunix Fri Jan 2 11:56:03 GMT 2015) 4.9.2"
-----------------------------------------------------------
So line 12 there handles the argc parameter into gen reg g1.
$ ./tzero 2 3 4 5
$ echo $?
5
looks correct but the source file still has no end of line. So I
wonder if zero or more lines is correct or not. The zero part I
mean.
dc
