3 ms·

Nope, it still links in crtfastmath: $ gcc -Ofast -fno-unsafe-math-optimizations -fpic -shared foo.c -o foo.so $ objdump -j .text --disassemble=set_fas

by moyix 4y ago

Nope, it still links in crtfastmath: $ gcc -Ofast -fno-unsafe-math-optimizations -fpic -shared foo.c -o foo.so $ objdump -j .text --disassemble=set_fast_math foo.so foo.so: file format elf64-x86-64 Disassembly of section .text: 0000000000001040 <set_fast_math>: 1040: f3 0f 1e fa endbr64 1044: 0f ae 5c 24 fc stmxcsr -0x4(%rsp) 1049: 81 4c 24 fc 40 80 00 orl $0x8040,-0x4(%rsp) 1050: 00 1051: 0f ae 54 24 fc ldmxcsr -0x4(%rsp) 1056: c3 retq

Night_Thastus 4y ago
Ouch. Two flags that should reasonably stop this, and neither do. This feels a bit like the time I was told "No, -wAll does not in fact add all warnings".
- speeder 4y ago
  Wait, it doesn't? O.o
  - moyix 4y ago
    Nope. clang has "-Weverything", and gcc has "-Wextra", both of which go beyond "-Wall". https://stackoverflow.com/questions/11714827/how-can-i-turn-on-literally-all-of-gccs-warnings https://stackoverflow.com/questions/11714827/how-can-i-turn-...
    - account42 4y ago
      -Wextra is also in Clang and is definitely not everything in either compiler. -Weverything is everything but that is only really useful to discover new warning flags (in combination with lots of -Wno...) for which you are better off reading GCC/Clang's release notes and/or documentation.
iforgotpassword 4y ago
Wait that other python package besides gevent you linked the according issue/pr "fixed" it by adding that flag. So I assumed "ok, -fno-fast-math doesn't override -Ofast, but then -fno-unsafe-math-optimizations surely does if they use this. No way they also just randomly add a flag and hope for the best" Do people ever actually test their fixes? Edit: right, via btrees: https://github.com/zopefoundation/BTrees/pull/179/files https://github.com/zopefoundation/BTrees/pull/179/files https://github.com/zopefoundation/meta/commit/2a33089508792e8d46186dbfcd8af093ab2249e7 https://github.com/zopefoundation/meta/commit/2a33089508792e...

by moyix 4y ago

Night_Thastus 4y ago

Ouch. Two flags that should reasonably stop this, and neither do. This feels a bit like the time I was told "No, -wAll does not in fact add all warnings".

speeder 4y ago
Wait, it doesn't? O.o
- moyix 4y ago
  Nope. clang has "-Weverything", and gcc has "-Wextra", both of which go beyond "-Wall". https://stackoverflow.com/questions/11714827/how-can-i-turn-on-literally-all-of-gccs-warnings https://stackoverflow.com/questions/11714827/how-can-i-turn-...
  - account42 4y ago
    -Wextra is also in Clang and is definitely not everything in either compiler. -Weverything is everything but that is only really useful to discover new warning flags (in combination with lots of -Wno...) for which you are better off reading GCC/Clang's release notes and/or documentation.

iforgotpassword 4y ago

Wait that other python package besides gevent you linked the according issue/pr "fixed" it by adding that flag. So I assumed "ok, -fno-fast-math doesn't override -Ofast, but then -fno-unsafe-math-optimizations surely does if they use this. No way they also just randomly add a flag and hope for the best" Do people ever actually test their fixes? Edit: right, via btrees: https://github.com/zopefoundation/BTrees/pull/179/files https://github.com/zopefoundation/BTrees/pull/179/files https://github.com/zopefoundation/meta/commit/2a33089508792e8d46186dbfcd8af093ab2249e7 https://github.com/zopefoundation/meta/commit/2a33089508792e...