I was able to reproduce the bug with the following code
(compile: g++ -Wall -O2 x.cpp)
#include <stdio.h>
#include <fstream>
typedef unsigned int Uint32;
inline Uint32 read_u32(std::istream& in)
{
Uint32 i;
in.read((char*)&i, 4);
return i;
}
inline float read_float(std::istream& in)
{
Uint32 u = read_u32(in);
return *(float*)(&u);
}
int main()
{
std::ifstream in("test");
for (int i = 0; i < 2; ++i) {
float x = read_float(in);
float y = read_float(in);
float z = read_float(in);
printf("x=%f y=%f z=%f\n", x, y, z);
}
return 0;
}
with this test file:
(hexdump test)
(2x the float values 1.0, nearly 1.0, and -1)
0000000 0000 3f80 ffff 3f7f 0000 bf80 0000 3f80
0000010 ffff 3f7f 0000 bf80
the output is:
x=0.000000 y=1.000000 z=1.000000
x=-1.000000 y=1.000000 z=1.000000
which is clearly wrong. the first x should be 1.0
In fact the values for x,y,z are all wrong, because the stored values
are 1,1,-1 in that order, not -1,1,1.
Compiling the code with -O1 gives the correct output.
Seems to have something to do with parameter order on the printf call or
something the like.
Hope this helps...
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