D - bug : float in a struct
- yaneurao sun-inet.or.jp (43/43) Jan 10 2004 phenomenon:
- Robert (101/104) Jan 10 2004 I guess that allocated sizes of global arrays are wrong
- Walter (3/46) Jan 10 2004 Can you be more specific? Exactly what fails?
- Robert (3/61) Jan 10 2004 Please read http://www.digitalmars.com/drn-bin/wwwnews?D/21511
- Walter (1/1) Jan 11 2004 Found the problem and fixed it. Thanks, guys. -Walter
phenomenon:
float is used in struct , and if long variable exists ahead of it ,
then a bad floating code would generate.
// invalid struct
struct a {
long a; // must be alignment to quad word ahead of float var.
float x,y,z,w;
}
// valid struct
struct b {
long a,b; // ok
float x,y,z,w;
}
// valid struct
struct c {
float x,y,z,w;
long a; // ok
}
here , simple example:
I test in WinXp.
// ---------------------------------------
private import std.c.stdlib;
struct i_part
{
long start;
float phase,r,g,b,a;
};
void i_rst(int i_x)
{
rays[i_x].phase=0.180*(float)(rand()%1000);
rays[i_x].r=0.001f*((float)(rand()%1000));
rays[i_x].g=0.001f*((float)(rand()%1000));
rays[i_x].b=0.001f*((float)(rand()%1000));
rays[i_x].a=0.0005f*((float)(rand()%1000));
}
i_part rays[100];
int main(){
for (int i=0;i<100;i++) i_rst(i);
for (int i=0;i<1;i++) {
int j = 0.0*(cast(float)i); // here , 'fistp [esp]' fails.
}
return 0;
}
Jan 10 2004
"Robert" <no spam.ne.jp>
I guess that allocated sizes of global arrays are wrong
when they have integers on the top and
floating points elsewhere.
==========================
struct Foo {
long a;
double b;
};
Foo array[4];
int main(){
char* str = " ";
printf("%p\n", &array[0]);
printf("%p\n", &array[3].b);
printf("%p\n", str);
return 0;
}
==========================
0040E090
0040E0C8
0040E0B8
==========================
" " and array[2].b have the same address 0040E0B8!
~~~~~~~~~~~~~~~~~~~~~~~~~~
struct Foo {
double a;
long b;
};
Foo array[4];
int main(){
char* str = " ";
printf("%p\n", &array[0]);
printf("%p\n", &array[3].b);
printf("%p\n", str);
return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~
0040E090
0040E0C8
0040E0D0
~~~~~~~~~~~~~~~~~~~~~~~~~~
It's OK.
<<<<<<<<<<<<<<<<<<<<<<<<<<
struct Foo {
long a;
long b;
};
Foo array[4];
int main(){
char* str = " ";
printf("%p\n", &array[0]);
printf("%p\n", &array[3].b);
printf("%p\n", str);
return 0;
}
<<<<<<<<<<<<<<<<<<<<<<<<<<
00410D10
00410D48
0040E080
<<<<<<<<<<<<<<<<<<<<<<<<<<
It's OK.
++++++++++++++++++++++++++
struct Foo {
long a;
double b;
long c;
};
Foo array[4];
int main(){
char* str = " ";
printf("%p\n", &array[0]);
printf("%p\n", &array[3].c);
printf("%p\n", str);
return 0;
}
++++++++++++++++++++++++++
0040E098
0040E0F0
0040E0C8
++++++++++++++++++++++++++
" " and array[2].a have the same address 0040E0F0!
struct Foo {
long a;
double b;
};
int main(){
foo(0);
return 0;
}
void foo(int a) {
Foo array[4];
int b;
printf("%p\n", &array[0]);
printf("%p\n", &array[3].b);
printf("%p\n", &a);
printf("%p\n", &b);
}
0012FEF0
0012FF28
0012FEEC
0012FF30
It's OK.
Jan 10 2004
Can you be more specific? Exactly what fails?
<yaneurao sun-inet.or.jp> wrote in message
news:bton25$18rg$1 digitaldaemon.com...
phenomenon:
float is used in struct , and if long variable exists ahead of it ,
then a bad floating code would generate.
// invalid struct
struct a {
long a; // must be alignment to quad word ahead of float var.
float x,y,z,w;
}
// valid struct
struct b {
long a,b; // ok
float x,y,z,w;
}
// valid struct
struct c {
float x,y,z,w;
long a; // ok
}
here , simple example:
I test in WinXp.
// ---------------------------------------
private import std.c.stdlib;
struct i_part
{
long start;
float phase,r,g,b,a;
};
void i_rst(int i_x)
{
rays[i_x].phase=0.180*(float)(rand()%1000);
rays[i_x].r=0.001f*((float)(rand()%1000));
rays[i_x].g=0.001f*((float)(rand()%1000));
rays[i_x].b=0.001f*((float)(rand()%1000));
rays[i_x].a=0.0005f*((float)(rand()%1000));
}
i_part rays[100];
int main(){
for (int i=0;i<100;i++) i_rst(i);
for (int i=0;i<1;i++) {
int j = 0.0*(cast(float)i); // here , 'fistp [esp]' fails.
}
return 0;
}
Jan 10 2004
Please read http://www.digitalmars.com/drn-bin/wwwnews?D/21511 "Walter" <walter digitalmars.com> wrote in message news:btpmuo$30b1$1 digitaldaemon.com...Can you be more specific? Exactly what fails? <yaneurao sun-inet.or.jp> wrote in message news:bton25$18rg$1 digitaldaemon.com...phenomenon: float is used in struct , and if long variable exists ahead of it , then a bad floating code would generate. // invalid struct struct a { long a; // must be alignment to quad word ahead of float var. float x,y,z,w; } // valid struct struct b { long a,b; // ok float x,y,z,w; } // valid struct struct c { float x,y,z,w; long a; // ok } here , simple example: I test in WinXp. // --------------------------------------- private import std.c.stdlib; struct i_part { long start; float phase,r,g,b,a; }; void i_rst(int i_x) { rays[i_x].phase=0.180*(float)(rand()%1000); rays[i_x].r=0.001f*((float)(rand()%1000)); rays[i_x].g=0.001f*((float)(rand()%1000)); rays[i_x].b=0.001f*((float)(rand()%1000)); rays[i_x].a=0.0005f*((float)(rand()%1000)); } i_part rays[100]; int main(){ for (int i=0;i<100;i++) i_rst(i); for (int i=0;i<1;i++) { int j = 0.0*(cast(float)i); // here , 'fistp [esp]' fails. } return 0; }
Jan 10 2004
Found the problem and fixed it. Thanks, guys. -Walter
Jan 11 2004