| Issue |
91224
|
| Summary |
When combined with Arm, floating point calculation results may be incorrect.
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
SakiTakamachi
|
Hi, I'm from php-src.
The following code:
```
// double.c
int main(void)
{
int i = 3;
double v = 0.03;
double v2 = 0.01;
double ret = v - (i * v2);
return 0;
}
```
compile:
```
clang -o double -g double.c
```
debug:
```
# gdb ./double
....
(gdb) b main
Breakpoint 1 at 0x724: file double.c, line 4.
(gdb) run
....
Breakpoint 1, main () at double.c:4
4 int i = 3;
(gdb) n
5 double v = 0.03;
(gdb)
6 double v2 = 0.01;
(gdb)
8 double ret = v - (i * v2);
(gdb)
10 return 0;
(gdb) p ret
$1 = -1.7347234759768071e-18
(gdb) p v
$2 = 0.029999999999999999
(gdb) p v2
$3 = 0.01
(gdb) p i
$4 = 3
(gdb) p i * v2
$5 = 0.029999999999999999
(gdb) p v - (i * v2)
$6 = 0
```
It is known that this phenomenon only occurs when using clang as the compiler and in an Arm environment.
(Sorry if the repository for the issue report is not appropriate)
version:
```
# clang -v
Ubuntu clang version 14.0.0-1ubuntu1.1
Target: aarch64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/11
Selected GCC installation: /usr/bin/../lib/gcc/aarch64-linux-gnu/11
Candidate multilib: .;@m64
Selected multilib: .;@m64
```
Regards
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