| Issue |
168788
|
| Summary |
C++ constexpr "library"? (not pre-compiled header)
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
jlmxyz
|
Hi
C++ constexpr is really a killer feature, allowing to create small byte code at compile time for everything that is deterministic, while allowing the same code to be used on what isn't deterministic.
In a way it's better than a template.
as template, and inline, they have the issue to be "recompiled" in each module they are used, this can increase the compile time and also make it difficult to share it in a library.
The compiler can also choose not to inline the function.
pre-compiled header don't match my needs
so I wonder if there is some compile option flag that could allow me to create a library (shared and static) providing my constexpr functions (aside my non constexpr functions) and pass it as an argument when compiling my modules
1. the constexpr function in library is assumed to be uptodate with the source in header (this is the role of the make system) once the library arg is provided.
2. if the function is used in module, and constexpr can be evaluated at compile time, then the compiler call the library function and use the result
3. if the function is used in module, and constexpr can't be evaluated at compile time
1. if the function is inline-able : the library code is copied in place, maybe modified to remove the function call overhead (argument creation and return value removal), don't know if there is a way in library to create functions that can't be called, but just stored, so without the overhead, in which case, the library act like a compiler cache, but not sure if it's something that is interesting or if the function should be usable and "dlopen-usable"
2. if the function is not inline-able : the symbol resolution is performed at link time as a regular library function
this will save lot of time in compilation, while taking full advantage of constexpr code optimization (size and speed)
thanks and regards
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