[PATCH RFC 2/3] gas: add a means to programmatically determine the assembler version

[Michael Matz]

Hello,

On Mon, 9 Dec 2024, Jan Beulich wrote:

> It has been more than once that I would have wanted to have a way to
> know the gas version in assembly sources, perhaps for use with .if. Add
> such a pre-defined symbol, yet key exposure to -v being used at least
> twice (three times to also emit the symbols to the symbol table).

Only defining the symbol with -vv or more is beyond quirky.  One would 
never be able to rely on these symbols in .s sources then, possibly except 
for test cases.  The common user wanting such symbol (for .if. or 
otherwise, which is very reasonable!) wouldn't know that those .s files 
need to be specifically assembled with -vv.  If the user learns of that, 
then that prints the version, so the user then needs to know even more, 
namely to use --silent.  Which then suppressed printing the version, but 
_not_ the emission of the symbols.

That's not a sensible interface :-)

Just define the symbols always, the usage of non-symbol chars should make 
all of this be reasonably non-conflicting with existing code.  If you 
decide that you absolutely _must_ have a cmdline option to control this, 
then don't make it be -v.  (I really think this should not depend on any 
options!)

Suggestion: make the symbols for .if. usage that are predefined be of a 
dependable format: e.g. 'GAS_DEFINED(foobar)' (where "foobar" would be the 
different names, but the whole string, including parens is the symbol).
That way the probability of conflicts with current code is about zero and 
the symbol names are somewhat systematic.


Ciao,
Michael.