🚀 go-pugleaf

Summary:
g++ doesn't clean up the stack after calling constructors, thus messing up
the stack and argument lists, as in fun(1, new Foo(..), 2)

Note: 
problem doesn't show (but is still there) if constructors are not used as 
actuals.

System:
g++ 1.36.1
Sun3, os3

----------------------------------------
[uw-larry - 1] % cat main.c
#include "stdio.h"

class Foo {
private:
    char* name;
public:
    Foo(char* s);
};


Foo::Foo(char* s) {
    name = s;
}


void fun(int a, Foo* f, int b) {
    printf("%d %d %d\n", a, (int)f, b);
}


main() {
    fun(1, new Foo("crash"), 2);
}
[uw-larry - 2] % g++ -v main.c
gcc version 1.36.1 (based on GCC 1.36)
 /usr/larry/users/klaiber/lib/gcc-cpp -+ -v -undef -D__GNUC__ -D__GNUG__ -D__cplusplus -Dmc68000 -Dsun -Dunix -D__mc68000__ -D__sun__ -D__unix__ -D__HAVE_68881__ -Dmc68020 main.c /usr/tmp/cca03962.cpp
GNU CPP version 1.36
 /usr/larry/users/klaiber/lib/gcc-cc1plus /usr/tmp/cca03962.cpp -quiet -dumpbase main.c -version -o /usr/tmp/cca03962.s
GNU C++ version 1.36.1 (based on GCC 1.36) (68k, MIT syntax) compiled by GNU C version 1.36.
default target switches: -m68020 -mc68020 -m68881 -mbitfield
 as -mc68020 -o main.o /usr/tmp/cca03962.s
 /usr/larry/users/klaiber/lib/gcc-ld -e start -dc -dp /lib/crt0.o /lib/Mcrt1.o main.o -lg++ /usr/larry/users/klaiber/lib/gcc-gnulib -lc
[uw-larry - 3] % a.out
1 148520 148520
         ^^^^^^
	 this is most definitely wrong!
----------------------------------------
Here's the generated assembly code: (w/o the -g option for readability)

#NO_APP
gcc_compiled.:
.text
	.even
.globl ___3FooPc
___3FooPc:
	link a6,#0
	movel a6@(8),a0
	movel a6@(12),a0@
	movel a0,d0
L1:
	unlk a6
	rts
LC0:
	.ascii "%d %d %d\12\0"
	.even
.globl _fun__FiP3Fooi
_fun__FiP3Fooi:
	link a6,#0
	movel a6@(16),sp@-
	movel a6@(12),sp@-
	movel a6@(8),sp@-
	pea LC0
	jbsr _printf
	addw #16,sp
L2:
	unlk a6
	rts
LC1:
	.ascii "crash\0"
	.even
.globl _main
_main:
	link a6,#0
	movel d2,sp@-
	jbsr ___main
	movel d0,d0
	pea 2:w
	pea LC1
	pea 4:w
	jbsr ___builtin_new
	addqw #4,sp
	movel d0,d2
	movel d2,sp@-
	jbsr ___3FooPc		<== **** PROBLEM right here ****
	movel d2,sp@-
	pea 1:w
	jbsr _fun__FiP3Fooi
	addw #20,sp
	clrl d0
	jra L3
L3:
	movel a6@(-4),d2
	unlk a6
	rts
----------------------------------------
The error is clear: after the jbsr, we ned an addqw #8,sp to pop the 2 args 
for Foo::Foo (this & s)

----------------------------------------
If a temporary variable is used, things seem to be fine:

[uw-larry - 4] % cat other.c
#include "stdio.h"

class Foo {
private:
    char* name;
public:
    Foo(char* s);
};


Foo::Foo(char* s) {
    name = s;
}


void fun(int a, Foo* f, int b) {
    printf("%d %d %d\n", a, (int)f, b);
}


main() {
    Foo* temp = new Foo("crash");
    fun(1, temp, 2);
}
[uw-larry - 5] % g++ -v other.c
gcc version 1.36.1 (based on GCC 1.36)
 /usr/larry/users/klaiber/lib/gcc-cpp -+ -v -undef -D__GNUC__ -D__GNUG__ -D__cplusplus -Dmc68000 -Dsun -Dunix -D__mc68000__ -D__sun__ -D__unix__ -D__HAVE_68881__ -Dmc68020 other.c /usr/tmp/cca03969.cpp
GNU CPP version 1.36
 /usr/larry/users/klaiber/lib/gcc-cc1plus /usr/tmp/cca03969.cpp -quiet -dumpbase other.c -version -o /usr/tmp/cca03969.s
GNU C++ version 1.36.1 (based on GCC 1.36) (68k, MIT syntax) compiled by GNU C version 1.36.
default target switches: -m68020 -mc68020 -m68881 -mbitfield
 as -mc68020 -o other.o /usr/tmp/cca03969.s
 /usr/larry/users/klaiber/lib/gcc-ld -e start -dc -dp /lib/crt0.o /lib/Mcrt1.o other.o -lg++ /usr/larry/users/klaiber/lib/gcc-gnulib -lc
[uw-larry - 6] % a.out
1 148520 2
        ^^^^
	it's the correct output allright
----------------------------------------


***HOWEVER***, as can be seen from the assembly code, g++ still doesn't
clean up the stack after the call to the constructor:


#NO_APP
gcc_compiled.:
.text
	.even
.globl ___3FooPc
___3FooPc:
	link a6,#0
	movel a6@(8),a0
	movel a6@(12),a0@
	movel a0,d0
L1:
	unlk a6
	rts
LC0:
	.ascii "%d %d %d\12\0"
	.even
.globl _fun__FiP3Fooi
_fun__FiP3Fooi:
	link a6,#0
	movel a6@(16),sp@-
	movel a6@(12),sp@-
	movel a6@(8),sp@-
	pea LC0
	jbsr _printf
	addw #16,sp
L2:
	unlk a6
	rts
LC1:
	.ascii "crash\0"
	.even
.globl _main
_main:
	link a6,#-4
	movel d2,sp@-
	jbsr ___main
	movel d0,d0
	pea LC1
	pea 4:w
	jbsr ___builtin_new
	addqw #4,sp
	movel d0,d2
	movel d2,sp@-
	jbsr ___3FooPc
	movel d2,a6@(-4)
	pea 2:w
	movel a6@(-4),sp@-
	pea 1:w
	jbsr _fun__FiP3Fooi
	addw #20,sp
	clrl d0
	jra L3
L3:
	movel a6@(-8),d2
	unlk a6
	rts
===========================================================================

PLEEEASE, try this and tell me whether you can reproduce the bug or whether
I have a screwed-up installation!  
A quick bug fix would be even more greatly appreciated!


	Alexander Klaiber
	klaiber@cs.washington.edu