Usability Improvements in GCC 15

Using a hierarchy to show template errors is brilliant and I'm sort of surprised compilers haven't always done that.

I was investigating C++-style templates for a hobby language of mine and SFINAE is an important property to make them work in realistic codebases, but leads to exactly this problem. When a compile error occurs, there isn't a single cause, or even a linear chain of causes, but an potentially arbitrarily large tree of them.

For example, it sees a call to foo() and there is a template foo(). It tries to instantiate that but the body of foo() calls bar(). It tries to resolve that and finds a template bar() which it tries to instantiate, and so on.

The compiler is basically searching the entire tree of possible instantiations/overloads and backtracking when it hits dead ends.

Showing that tree as a tree makes a lot of sense.

Usability improvement request for this article: don't hijack the browser back button :P

With GCC error messages usually the only part I wanna see is "required from here" and yet it spams zillions of "note: ...". With the nesting enabled, it's way easier to read --- just look at the top indentation level. Hooray!!!

I hope gcc remains the default in Linux due to the GPL. But I expect someday clang will become the default.

Plus I heard COBOL was merged in with the compiler collection, nice!

Big fan of all of this except for the emojis in my console

Please gcc, let me have a `~/.config/gcc` config file or an ENV variable so I can ask for single lined error messages.

I literally do not need ascii art to point to my error, just tell me line:col and a unique looking error message so I can spend no more than 1 second understanding what went wrong

Also allow me to extend requires with my own error messages. I know it'll be non standard but it would be very nice tyvm

The template error messages look great. I wonder if it’s worth writing a translator from clang/gcc messages to these ones, for users of clang and older gcc (to pipe one’s error messages to)

I can't imagine a piece of software easier to use than gcc 3.4.6, sorry.

We are now entering a Rococo period of unnecessarily ornate compiler diagnostics.

Getting these elaborate things to work is a nice puzzle, like Leetcode or Advent of Code --- but does it have to be merged?

I'm all up for better error messaging. :)

Can't use Clang where I'm at, but I do get to use fairly cutting-edge GCC, at least for Windows development. So I may get to see these improvements once they drop into MSYS.

The writer David Malcolm tells a story in his article about compiling C17 code and pretending it's C23. Duh, no wonder it breaks!

You C standard authors have it bass-ackwards. The version of the code must accompany the code, not the compiler invocation.

Why all this waste in Unicode art that nobody will ever see and that confuses your IDE.

Why not spend time on helping IDEs to understand error messages? That would be billion times more useful.

What is the status of GCC plugins?

Here's the pending GCC 15 release notes: https://gcc.gnu.org/gcc-15/changes.html (since the link in the article points to GCC 14)

- I'd love to see godbolt examples of the sort of optimizations [[unsequenced]] and [[reproducible]] can do.

- GCC has always been in my experience smart enough to know how to optimize normal C code into ROL and ROR instructions. I've never had any issues with it. So what's the point of __builtin_stdc_rotate_left()? Why create a builtin when it is not needed? What I wish GCC and Clang would do instead, is formally document the magic ANSI C89 incantations that trigger the optimization, e.g. `#define ROL(x, n) (((x) << (n)) | ((x) >> (64 - (n))))`. That way we can have clean portable code with less #ifdef hell along with assurances it'll go fast when -O is passed.

- What is "Abs Without Undefined Behavior (addition of builtins for use in future C library <stdlib.h> headers)."?

- What is "Allow zero length operations on null pointers"?

- Re: "Introduce complex literals." How about some __int128 literals?

- "The "redzone" clobber is now allowed in inline assembler statements" wooo I've wanted something like this for a while.

Great work from the greatest compiler team!

Already looking forward to `grep`ing warning emojis in output. What's next? Poop emoji for errors?

I like a these modernization efforts in GCC, a lot of old niggles are gone now, and they've made a lot of new improvements I didn't think were possible/easy!