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Compiler Explorer
@compiler-explorer.com
1.3K followers 30 following 15 posts
A website for exploring the output of compilers. aka godbolt.org
Supports C, C++, Rust, Fortran, COBOL and many many more.
Support us at https://patreon.com/mattgodbolt
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compiler-explorer.com
Compiler Explorer @compiler-explorer.com · Jul 23
CE relies on your support! How you can help:

* Submit PRs & report issues: github.com/compiler-exp...
* Become a Patron: patreon.com/mattgodbolt
* Sponsor us: github.com/sponsors/com...
* Buy CE swag: shop.compiler-explorer.com
* Join our Discord: discord.gg/B5WacA7
github.com
Reposted by Compiler Explorer
matt.godbolt.org
This December, I'll be posting an article & video each day until Christmas in the Advent of Compiler Optimisations! #AoCO2025
Each day we'll explore a fun optimisation in C or C++; some low-level, x86 or ARM-specific, some high-level. Hope you'll join me!
YT: youtube.com/mattgodbolt
Blog: xania.org
Matt Godbolt’s blog
xania.org
November 13, 2025 at 7:51 PM
compiler-explorer.com
Investigating why Windows compilers are down! Watch this space, and sorry for any inconvenience -mg
October 7, 2025 at 2:30 PM
Reposted by Compiler Explorer
matt.godbolt.org
LLM-explanation is now live in @compiler-explorer.com - An example: compiler-explorer.com/z/rvvx7MxKq

* LLMs make mistakes and are overconfident
* We'll never force LLMs or AI on you, it's opt in (like clang-tidy, PVS Studio or other tools)
* It is *beta* quality

Initial results are promising(1/3)
Compiler Explorer - C++ (x86-64 clang 21.1.0)
// setup constexpr auto valid_chars = "0123456789abcdef"; bool is_valid_id(std::string_view maybe_id) { if (maybe_id.size() != 16) { return false; } if (maybe_id.find_first_not_of(valid_ch...
explain.compiler-explorer.com
September 21, 2025 at 10:54 PM
Reposted by Compiler Explorer
matt.godbolt.org
@compiler-explorer.com is now running with a completely new storage mechanism in the back end. It's taken me quite a long time to get to the point where I felt confident enough to switch over to it and it seems like it's gone without a hitch. Details:
xania.org/202509/cefs
CEFS: Finally Solving CE's Mount(ing) Problems — Matt Godbolt’s blog
In which CE's boot times are finally brought under control
xania.org
September 11, 2025 at 9:35 PM
Reposted by Compiler Explorer
matt.godbolt.org
Hey folks! @compiler-explorer.com is free & open for everyone, but if you're planning to use our API for bulk executions though, please ping us! CE is a shared resource and heavy use can slow things down for the whole community. DM me to chat - happy to help figure out what works for everyone! :)
August 22, 2025 at 8:18 PM
compiler-explorer.com
Support friend of the site Jason by going to one of his excellent courses! Jason was instrumental in publicising CE in the early days and his courses are awesome too! -mg
lefticus.bsky.social Jason Turner @lefticus.bsky.social · Aug 22
Come to one of my highly interactive and dynamic C++ Best Practices conference workshops this year at CppCon (Sept 13-14) or NDC TechTown (Sept 22-23)

Only about 4 weeks left!

ndctechtown.com/workshops/c-...

cppcon.org/class-2025-b...
C++ Best Practices | NDC TechTown 2025
This is a 2-day workshop that explores Best Practices as they apply to C++.
ndctechtown.com
August 22, 2025 at 10:47 PM
compiler-explorer.com
CE relies on your support! How you can help:

* Submit PRs & report issues: github.com/compiler-exp...
* Become a Patron: patreon.com/mattgodbolt
* Sponsor us: github.com/sponsors/com...
* Buy CE swag: shop.compiler-explorer.com
* Join our Discord: discord.gg/B5WacA7
github.com
July 23, 2025 at 11:21 PM
Reposted by Compiler Explorer
matt.godbolt.org
I've been getting more anecdotal reports that @compiler-explorer.com is slow. Seems to be folks' simple code taking a while, likely queued up behind a longer compile. We've done some digging and it seems to have gotten worse since December last year. Doesn't seem to be bot traffic. Have you noticed?
July 19, 2025 at 11:08 PM
compiler-explorer.com
Huge news! AWS has approved Compiler Explorer for their Open Source Credits program, covering our infrastructure costs for the next year!
Thank you AWS for supporting open source! This means faster compiles, better queuing & more improvements coming. Exciting times ahead!
June 30, 2025 at 6:37 PM
Reposted by Compiler Explorer
matt.godbolt.org
I'm frequently asked "how much does @compiler-explorer.com cost to run". I've done some digging and posted xania.org/202506/compi... which is a high-level breakdown of the costs (and revenue); and links to a more in depth report if you want all the gory details.
Compiler Explorer Cost Transparency — Matt Godbolt’s blog
In which I try and show how we spend your kind Patreon donations
xania.org
June 11, 2025 at 1:07 PM
Reposted by Compiler Explorer
matt.godbolt.org
I'm half way through my career break, and taking stock. Plan was to do conf talks (check), work on @compiler-explorer.com (check), spend time with family (sort of) and even do some hobby code (also sort of). Higher level goal still is to get CE "on its feet" a bit...
June 8, 2025 at 2:27 PM
Reposted by Compiler Explorer
matt.godbolt.org
A fantastic walk through of some @compiler-explorer.com features by one of our core maintainers @ofekshilon.bsky.social . Thanks Ofek!

youtu.be/_9sGKcvT-TA
Get More Out of Compiler-Explorer ('godbolt') :: Ofek Shilon
YouTube video by CoreCppIL
youtu.be
June 5, 2025 at 10:17 PM
Reposted by Compiler Explorer
matt.godbolt.org
It's been a while since I've written about the innards of @compiler-explorer.com. xania.org/202506/how-c... has the details, some statistics and some fun war stories.
How Compiler Explorer Works in 2025 — Matt Godbolt’s blog
How we handle 92 million compilations a year without everything catching fire
xania.org
June 3, 2025 at 9:41 PM
Reposted by Compiler Explorer
matt.godbolt.org
On @compiler-explorer.com URLs and another Google product sunsetting: xania.org/202505/compi...
Compiler Explorer and the Promise of URLs That Last Forever — Matt Godbolt’s blog
How we're preserving 12,000 legacy links as Google's URL shortener rides into the sunset
xania.org
May 28, 2025 at 3:32 PM
Reposted by Compiler Explorer
matt.godbolt.org
Experimenting with something like this for @compiler-explorer.com - wondering what your thoughts are? AI is getting everywhere, and can be divisive. I'm hoping something like this - so long as I can get the output quality high enough - is a net benefit to help folks learn more about their code.
A screenshot of Compiler Explorer showing an "AI Explain this" view. The source code is: bool isspc(char c) { return c == '\n' || c == '\r' || c == '\t' || c == ' '; } The asm is: isspc(char): mov ecx, edi cmp cl, 33 setb dl movabs rax, 4294977024 shr rax, cl and al, dl ret Below is a "Claude Explain" window with: The function isspc(char) is compiled to an efficient bit manipulation technique to check for whitespace characters. Let's break down the assembly instructions: mov ecx, edi Copies the input character from the edi register (first function argument) to ecx cl will contain the lowest 8 bits (the character) cmp cl, 33 Compares the character against decimal 33 This is a preliminary check to quickly filter out non-whitespace characters setb dl Sets the dl register to 1 if the character is below 33 (space, tab, newline, etc.) Uses a conditional set instruction movabs rax, 4294977024 Loads a pre-computed 64-bit constant This constant represents a bit mask for whitespace detection shr rax, cl Shifts the bit mask right by the character's value This dynamically positions the mask based on the input character and al, dl Performs a bitwise AND between the shifted mask and the previous condition Produces the final boolean result in al ret Returns the result (0 or 1) in al This implementation is a highly optimized branchless method for checking whitespace characters, using bit manipulation instead of multiple comparisons. It avoids conditional jumps, which can be slower on modern CPUs. The code checks for space (' '), newline ('\n'), carriage return ('\r'), and tab ('\t') in a single, efficient operation.
May 23, 2025 at 8:09 PM
Reposted by Compiler Explorer
matt.godbolt.org
Thrilled to share that @compiler-explorer.com has received a $10K grant from NVIDIA's FOSS Fund! This support will help keep our GPU instances running and allow developers worldwide to experiment with CUDA code. Thank you NVIDIA AI Dev for supporting open source tools! #NVIDIAGrant
April 23, 2025 at 10:23 PM
Reposted by Compiler Explorer
shafik.bsky.social
Once again

#programming
Bernie once again meme with I am once again asking you to remember that if turning on optimizations changes the behavior of your program, it is likely you are missing some undefined behavior
February 8, 2025 at 7:51 PM
compiler-explorer.com
We just blocked a TW-based IPv6 address from making many many back-to-back requests, most of which seemed to hit our caches (and thus were duplicates). If this affected you, please DM us or reply and we can help diagnose what went wrong. -mg
January 6, 2025 at 12:22 AM
compiler-explorer.com
Compiler Explorer in 2024!

0.017 cents per compilation for 190M compilations. Tons of new features, Matt takes stock:

www.patreon.com/posts/compil...
Compiler Explorer in 2024 | Matt Godbolt
Get more from Matt Godbolt on Patreon
www.patreon.com
December 31, 2024 at 12:51 PM
Reposted by Compiler Explorer
matt.godbolt.org
Sent my first proper Patreon/GitHub sponsor update for @compiler-explorer.com work today. Surreal experience, I'm kinda giving my first update to my new boss(es) :-)
December 7, 2024 at 8:40 PM
Reposted by Compiler Explorer
shader-slang.bsky.social
Godbolt now has Slang support!

godbolt.org
@compiler-explorer.com
Compiler Explorer
Compiler Explorer is an interactive online compiler which shows the assembly output of compiled C++, Rust, Go (and many more) code.
godbolt.org
December 5, 2024 at 5:57 PM
Reposted by Compiler Explorer
matt.godbolt.org
So, after over 5 years at Aquatic, I made the tough call to leave and try something else. I had a wonderful time there, enjoyed the work and made some great friends. I'll be taking some time between jobs and will be working on @compiler-explorer.com and other OSS projects. I'm excited!
November 22, 2024 at 9:06 PM
Reposted by Compiler Explorer
matt.godbolt.org
Only 2 days left 15% off stuff at the CE shop. I just uploaded a dark-friendly logo too! Get some stuff to show off your love of CE and know you're helping the site at the same time!
compiler-explorer.myspreadshop.com
Compiler Explorer
Support Compiler Explorer by buying awesome branded kit!
compiler-explorer.myspreadshop.com
November 23, 2024 at 10:48 PM
compiler-explorer.com
Investigating a DDoS attack (looks like script kiddies again). Getting a bunch of weird POSTs to our noscript API. Site is handling it but it's alerting me, so have temporarily blocked some things. Apologies if you're caught in the crossfire! -mg
November 17, 2024 at 2:28 AM
Reposted by Compiler Explorer
matt.godbolt.org
We have so many compilers on @compiler-explorer.com that the "configuration JSON" we send on /every pageload/ totals 60GiB/day (!!)
I think we can probably do better...
November 12, 2024 at 4:41 AM