based on #24127
Needs some tweaks to replace the other `struct` type generations, e.g.
seqs, maybe by exposing `BaseTypeKind` as a parameter. C++ and
codegenDecl etc seem like they are going to need attention.
Also `Builder` should really be `distinct string` that one has to call
`extract` on, but for this to be optimal in the current codegen, we
would need something like:
```nim
template buildInto(s: var string, builderName: untyped, body) =
template `builderName`: untyped = Builder(s)
body
buildInto(result, builder):
builder.add ...
```
but this could be a separate PR since it might not work with the
compiler. The possibly-not-optimal alternative is to do:
```nim
template build(builderName: untyped, body): string =
var `builderName` = Builder("")
body
extract(`builderName`)
result = build(builder):
builder.add ...
```
where the compiler maybe copies the built string but shouldn't.
---------
Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>
…instantiations (C/C++ backend)
AFAIK, #22802 expanded `noinit`'s utility by allowing the pragma to be
attached to types (thanks @jmgomez !).
I suggest broadening the scope a bit further: try to avoid `nimZeroMem`s
on a type level beyond imported C/C++ types[^1], saving us from
annotating the type instantiations with `noinit`.
If this change is deemed acceptable, I will also adjust the docs, of
course.
Adding tests for this change seems a bit problematic, as the effect of
this type annotation will be to work with uninitialized memory, which
*might* match 0 patterns.
[^1]: "complex value types" as already defined here:
94c5996877/compiler/cgen.nim (L470-L471)
the function name extension encoded by paths could be useful for
debugging where the function is from
Before:
```js
function newSeq_33556909(len_33556911)
```
After:
```js
function newSeq__system_u2477(len_p0)
```
This is just one of those tiny steps towards the goal of an "optimized"
C and C++ codegen I raised elsewhere before - what does me babbling
"optimized" mainly entail?
(not mutually-exclusive ascertainment proposals following:)
- less and simplified resulting code: easier to pick up/grasp for the
C/C++ compiler for to do its own optimization heuristics, less parsing
effort for us mere humans trying to debug, especially in the case of
interop
- build time reduction: less code emission I/O, runtime string
formatting for output...
- easier access for fresh contributors and better maintainability
- interop improvements
- further runtime optimizations
I am eagerly looking forward to the results of the LLVM-based
undertakings, but I also think we can do a bit better (as outlined
above) with our current C/C++ backends till those come to fruition.
**Long story short**: this PR here focuses on the C++ backend,
augmenting the current codegen method of establishing "temporary"
variables by using C++11's auto type deduction. The reasons for adopting
an "Almost Always Auto" style have been collected [here
](https://herbsutter.com/2013/08/12/gotw-94-solution-aaa-style-almost-always-auto/)
for the C++ world. For those hopping between C++'s and Nim's realms,
this change also results in a bit less code and less work for the
codegen part (no redundant `getTypeDesc`s): no need to tell the C++
compiler the type it already knows of (in most cases).
fixes#22909
required by https://github.com/nim-lang/Nim/pull/23267
```nim
proc foo: string =
assert false
result = ""
```
In the function `foo`, `assert false` raises an exception, which can
cause `result` to be uninitialized if the default result initialization
is optimized out
fixes#22597
```nim
proc autoToOpenArray*[T](s: Slice[T]): openArray[T] =
echo "here twice"
result = toOpenArray(s.p, s.first, s.last)
```
For functions returning openarray types, `fixupCall` creates a temporary
variable to store the return value: `let tmp = autoToOpenArray()`. But
`genOpenArrayConv` cannot handle openarray assignements with side
effects. It should have stored the right part of the assignment first
instead of calling the right part twice.
**TODO**
- [x] fixes changelog
With the new option `nimPreviewVtables`, `methods` are confined in the
same module where the type of the first parameter is defined
- [x] make it opt in after CI checks its feasibility
## In the following-up PRs
- [ ] in the following PRs, refactor code into a more efficient one
- [ ] cpp needs special treatments since it cannot embed array in light
of the preceding limits: ref
https://github.com/nim-lang/Nim/pull/20977#discussion_r1035528927; we
can support cpp backends with vtable implementations later on the
comprise that uses indirect vtable access
---------
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>
Theoretical Benefits / Plans:
- Typed assembler-like language.
- Allows for a CPS transformation.
- Can replace the existing C backend by a new C backend.
- Can replace the VM.
- Can do more effective "not nil" checking and static array bounds
checking.
- Can be used instead of the DFA.
- Easily translatable to LLVM.
- Reasonably easy to produce native code from.
- Tiny memory consumption. No pointers, no cry.
**In very early stages of development.**
Todo:
- [x] Map Nim types to IR types.
- [ ] Map Nim AST to IR instructions:
- [x] Map bitsets to bitops.
- [ ] Implement string cases.
- [ ] Implement range and index checks.
- [x] Implement `default(T)` builtin.
- [x] Implement multi string concat.
- [ ] Write some analysis passes.
- [ ] Write a backend.
- [x] Integrate into the compilation pipeline.
* [C++] Member pragma RFC #530
rebase devel
* changes the test so `echo` is not used before Nim is init
* rebase devel
* fixes Error: use explicit initialization of X for clarity [Uninit]
* implements: [C++] constructor pragma improvement (fix#21921)
t
* fix test so it doesnt use echo in globals
* Update compiler/ccgtypes.nim
* Update lib/std/private/dragonbox.nim
---------
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>
