DIP41
Contents
DIP 41: dmd command line overhaul. (still editing : don't read yet)
| Title: | dmd command line overhaul. |
|---|---|
| DIP: | 41 |
| Version: | 1 |
| Status: | Draft |
| Created: | 2013-05-20 |
| Last Modified: | 2013-05-20 |
| Author: | Timothee Cour |
| Links: | dmd command line options bad design: -offilename, -Ddocdir etc. |
Abstract
This DIP seeks to improve dmd's command line flags, to make it more consistent with other tools, more expandable, and better interact with other tools such as rdmd.
-offilename vs -of=filename
Dmd currently uses 2 conventions for its flags with arguments:
- type A: -offilename, -Dddocdir, -Dffilename, -Ipath (etc)
- type B: -version=ident (etc)
Type A, the most common in dmd, is problematic:
- it doesn't scale: we can't have any new flag starting with "-I" or "-L", etc as it would create conflicts.
- it's visually harder to tell from the command line the options from the arguments to these options
- it's using a different (worst) convention from most other tools (including other D compilers, like gdc or ldc)
For reference, ldc uses: -of=filename, -Dd=docdir, -Df=filename, -I=path etc.
Deprecation path
We should support type B convention for all flags in a future release of dmd, and support the existing ones for some time until they become deprecated.
1) Make all future flags have type B.
2) Migrate all A flags to B flags. Here's one possible way to achieve this (say in next dmd release):
dmd -offilename main.d //works but generates a warning for now, and error in a subsequent dmd release dmd -old_flag -offilename main.d //works and doesn't generate a warning. dmd -new_flag -of=filename main.d //works. After a certain time passed, -new_flag is implied
Note, A and B flags can't be mixed, eg: -offilename -Ddoc=dir will give error, in all 3 cases above (ie for flags that are currently in the A style).
2b) Alternative: use a new binary name (dmd2, reminds of D2, ldc2, ldmd2) instead of -newflag. I don't like this as much somehow.
3) can we deprecate the current behavior where one can pass the file name without extension (main vs main.d) as source? Consistency is better than avoiding to type those 2 characters. I created a pathological case with main.d is conflicting with main.d.d (with different contents). Which one do you think is called when we call rdmd main.d ? Note, I raised a very analogous concern here [1] regarding naming of object files in a flat hierarchy (see my example with dmd -c -oq foo/mod.d foo_mod.d)
4) The current strategy of rdmd is to treat as input arguments anything after the first source file: rdmd main.d myfirstprogramarg // a bit awkward, especially with optional extension it gets hard to parse visually.
This is error prone, and inconsistent with dmd's behavior, which is: dmd src1.d -run main.d myfirstprogramarg //a bit awkward, need to split the source from the main file.
I suggest instead something simpler, explicit and consistent, using -args as a dmd command line argument, that would just work as well with rdmd:
dmd main.d src1.d -args myfirstprogramarg rdmd main.d -args myfirstprogramarg
5) currently we distinguish rdmd's arguments from dmd's arguments via '--' vs '-'. A better way IMO would be to have a special flag indicating the start of dmd's (or gdc/ldc...) flags: eg rdmd --chatty --dflags -version=myversion main.d
Notes: Has support of Walter (here)
