Make poll() the default

[falbrechtskirchinger]

poll() is available on:

• AIX
• FreeBSD
• Genode
• Haiku
• HP-UX
• Illumos/Solaris
• Linux
• MINIX 3
• MacOSX
• OpenBSD
• Plan 9
• QNX
• RTEMS
• VxWorks
• Windows
• Zephyr
• z/OS USS

poll() is not available on:

• NonStop OS
• OpenVMS

select() can still be enabled by defining CPPHTTPLIB_USE_SELECT.

Most users likely won't see any performance improvements (or the contrary), but the WebSockets code may see a minuscule improvement.

[yhirose]

@falbrechtskirchinger this suggestion sounds good to me.

@alex-cornford, as far as I know, you are the only user that uses OpenVMS. So once I accept this pull request, you will have to define CPPHTTPLIB_USE_SELECT from the next version. :)

[yhirose]

@falbrechtskirchinger I am fine to change the default behavior from select to poll, but select support is still very important to me.

My biggest concern with this pull request is that select is no longer tested at all on GitHub Actions CI. Could you make necessary changes to the GitHub Actions Workflow files to run the unit test suite with select on all the platform? I know it will cause the testing time double, but it's absolutely necessary cost. Thanks!

[falbrechtskirchinger]

My biggest concern with this pull request is that select is no longer tested at all on GitHub Actions CI. Could you make necessary changes to the GitHub Actions Workflow files to run the unit test suite with select on all the platform? I know it will cause the testing time double, but it's absolutely necessary cost. Thanks!

Agreed. I was worried that poll() hadn't been tested before, so testing both is a good idea. 20 jobs can run in parallel, so test time shouldn't be longer.

[falbrechtskirchinger]

@sum01 @abouvier @jimmy-park @Tachi107 I'm sure @yhirose would appreciate you looking over the CMake changes in this PR. I've added an option HTTPLIB_USE_SELECT which defines CPPHTTPLIB_USE_SELECT. Thanks!

[falbrechtskirchinger]

@yhirose All builds output the command line now (added /v:m /clp:ShowCommandLine /nologo to Windows builds). You can verify that CPPHTTPLIB_USE_SELECT is defined where needed.

[yhirose]

Looks great!

[Tachi107]

Poll is already enabled in the Debian cpp-httplib package, so it is already widely deployed :)

Note to self (or to whoever wants to do so): the option should also be added to the meson build scripts

[falbrechtskirchinger]

Poll is already enabled in the Debian cpp-httplib package, so it is already widely deployed :)

Good to hear. Shockingly the Gentoo ebuild doesn't enable it.

Note to self (or to whoever wants to do so): the option should also be added to the meson build scripts

I didn't care enough to add an option for the archaic select(). Is meson even available on any OS that doesn't have poll()? Does meson run without poll()? 😆

[Tachi107]

Il 18 febbraio 2025 13:07:53 CET, Florian Albrechtskirchinger ***@***.***> ha scritto:

falbrechtskirchinger left a comment (yhirose/cpp-httplib#2065) I didn't care enough to add an option for the archaic `select()`. Is meson even available on any OS that doesn't have `poll()`? Does meson run without `poll()`? 😆

Yeah, makes sense! Maybe it should just enable it by default, or when poll is detected on the system. Will do.

[alex-cornford]

@falbrechtskirchinger this suggestion sounds good to me.

@alex-cornford, as far as I know, you are the only user that uses OpenVMS. So once I accept this pull request, you will have to define CPPHTTPLIB_USE_SELECT from the next version. :)

@yhirose OpenVMS builds and runs with and without CPPHTTPLIB_USE_SELECT defined.

[falbrechtskirchinger]

@falbrechtskirchinger this suggestion sounds good to me.
@alex-cornford, as far as I know, you are the only user that uses OpenVMS. So once I accept this pull request, you will have to define CPPHTTPLIB_USE_SELECT from the next version. :)

@yhirose OpenVMS builds and runs with and without CPPHTTPLIB_USE_SELECT defined.

@alex-cornford Great! So, am I just misinformed then and OpenVMS does have poll() or did I make a mistake? Adding some print statements to check...

Edit: No, it's definitely using poll() by default and select() with CPPHTTPLIB_USE_SELECT defined. 👍

[alex-cornford]

@falbrechtskirchinger this suggestion sounds good to me.
@alex-cornford, as far as I know, you are the only user that uses OpenVMS. So once I accept this pull request, you will have to define CPPHTTPLIB_USE_SELECT from the next version. :)

@yhirose OpenVMS builds and runs with and without CPPHTTPLIB_USE_SELECT defined.

@alex-cornford Great! So, am I just misinformed then and OpenVMS does have poll() or did I make a mistake? Adding some print statements to check...

Edit: No, it's definitely using poll() by default and select() with CPPHTTPLIB_USE_SELECT defined. 👍

The OpenVMS C++ compiler supports poll() and select(). I don't know how it works internally.

[yhirose]

@falbrechtskirchinger according to your list, 'NonStop OS' is the only environment and I don't think there is any user using cpp-httplib on the OS. So I am now thinking of going further, which means removing select() completely and using poll() only. It can simplify the code and reduce my maintenance cost. What do you think?

[falbrechtskirchinger]

@falbrechtskirchinger according to your list, 'NonStop OS' is the only environment and I don't think there is any user using cpp-httplib on the OS. So I am now thinking of going further, which means removing select() completely and using poll() only. It can simplify the code and reduce my maintenance cost. What do you think?

@yhirose I have double-checked my list since I was wrong about OpenVMS.

• VxWorks only has select() (it has several functions including the word poll, which threw off my search).
• I've re-confirmed some of the other ones, I was less sure about: RTEMS (only since 2021), QNX, Zephyr
• Genode and NonStop OS have neither select() nor poll().

So, it's only VxWorks, AFAICT. But, cpp-httplib doesn't build on VxWorks right now anyway:

#  ifdef VXWORKS
#   include <sockLib.h>
#   include <selectLib.h>

https://www.ee.torontomu.ca/~courses/ee8205/Data-Sheets/Tornado-VxWorks/vxworks/ref/selectLib.html#select

Removing select() doesn't seem unreasonable. Just give me the go-ahead, and I'll submit a PR.

[yhirose]

Removing select() doesn't seem unreasonable. Just give me the go-ahead, and I'll submit a PR.

Good. Could you please proceed to make the change? Thanks a lot!