| Issue |
179695
|
| Summary |
clang -Og takes 2 minutes to build a C program vs 6 seconds for clang -O3, and uses 1.8 GiB of memory
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
vstinner
|
Building (the main branch of) Python with clang 21 fails randomly with a timeout of 20 minutes. I identified that the build is especially slow for `Python/ceval.c` and `Modules/_testinternalcapi/interpreter.c`. I built `interpreter.c` with `-E` to create a reproducer:
**Reproducer:** [bug.c](https://github.com/user-attachments/files/25076295/bug.c)
On my Fedora 43 laptop (x86-64) with **clang 21**.1.8:
* -O3: `time clang -c -O3 bug.c -o bug` takes 6 seconds
* -Og: `time clang -c -Og bug.c -o bug` takes **2 minutes 45 seconds** and consumes up to 1,8 GiB of RSS memory
`clang -O0`, `clang -O1` and `clang -O2` take between 1 and 6 seconds.
I cannot reproduce this issue on a ppc64le machine with **clang 20**.1.8:
* -Og: 17.5 seconds
* -O3: 18.9 seconds
How can I help you to debug this issue?
I'm trying to reduce the reproducer program, but so far I failed to reduce the `Test_EvalFrame()` function (17k lines).
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