Libc: fix ef_exp.s by Bughunter #177

IgorA · 2025-03-21T22:20:39+01:00

IgorA commented

2025-03-21 22:20:39 +01:00

this bug was fixed by Kirilom (by Bughunter) 5 years ago in another similar file

<img width="650" alt="image.png" src="attachments/e2d58257-9103-49fe-ad2a-868a8cb39982"> this bug was fixed by Kirilom (by Bughunter) 5 years ago in another similar file

image.png

43 KiB

IgorA added 1 commit 2025-03-21 22:20:42 +01:00

Libc: fix ef_exp.s by Bughunter

Build system / Check kernel codestyle (pull_request) Successful in 28s

Details

Build system / Build (pull_request) Successful in 5m23s

Details

d5c1325b02

dunkaist commented

2025-03-21 22:50:31 +01:00

menuetlibc: Fix floating exponent calculation

The fix was initially done by Bughunter in 12a6b7f2 (r7958) for double.
This commit applies the same fix to the float exponent.

menuetlibc: Fix floating exponent calculation The fix was initially done by Bughunter in 12a6b7f2 (r7958) for double. This commit applies the same fix to the float exponent.

IgorA commented

2025-03-22 00:27:13 +01:00

The input parameters of the function are in different formats (4 or 8 bytes).

The algorithm of operation must be the same, because the FPU registers are 80 bits. After exiting the function, the result is converted to 4 or 8 bytes. It is impossible to finally test the correctness of the expf (float) function because the expf function is not exported from the libc library.

The input parameters of the function are in different formats (4 or 8 bytes). <img width="623" alt="image.png" src="attachments/208e1078-ae3a-4fa1-bb47-7e0c78c8896f"> The algorithm of operation must be the same, because the FPU registers are 80 bits. After exiting the function, the result is converted to 4 or 8 bytes. It is impossible to finally test the correctness of the expf (float) function because the expf function is not exported from the libc library. <img width="125" alt="image.png" src="attachments/c8845d2d-c3ca-4128-864b-d8c141284e4a">

image.png

19 KiB

image.png

2.6 KiB

mxlgv commented

2025-03-22 10:00:17 +01:00

@IgorA There seems to be no point in this fix since menuetlibc is deprecated.
In libc.obj, the mathematics was taken from here, perhaps there is also a bug there: https://git.kolibrios.org/KolibriOS/kolibrios/src/branch/main/programs/develop/ktcc/trunk/libc.obj/source/math

@IgorA There seems to be no point in this fix since `menuetlibc` is deprecated. In `libc.obj`, the mathematics was taken from here, perhaps there is also a bug there: https://git.kolibrios.org/KolibriOS/kolibrios/src/branch/main/programs/develop/ktcc/trunk/libc.obj/source/math

mxlgv added the

PR

Review required

label 2025-03-22 10:00:52 +01:00

IgorA commented

2025-03-22 13:37:57 +01:00

I made a test program and found that after revision 9842 the exp function was broken.

test in excel:

I made a test program and found that after revision 9842 the exp function was broken. <img width="443" alt="image.png" src="attachments/ebee91c1-0f9c-4f9a-a193-fca5a227a519"> <img width="443" alt="image.png" src="attachments/ec45fc13-5f84-49dc-bed7-65975e9d3f62"> test in excel: <img width="306" alt="image.png" src="attachments/bd85af4d-fb60-4a0e-9fd1-e649b2fe4807">

image.png

14 KiB

image.png

13 KiB

image.png

9.3 KiB

Sweetbread force-pushed libc-fix from d5c1325b02 to 3c547b217f

2025-03-30 16:48:17 +02:00

Compare

mxlgv approved these changes 2025-04-02 20:17:39 +02:00

mxlgv added

PR