[Rpm-maint] [rpm-software-management/rpm] Macro Language - tips, best reference ? (Discussion #2094)

[JVDptt]

Or, more simply:

v4.17.0:

$ rpm --eval '%define is_enabled() %{expr "%{%1}"=="1"?"%2":"%3"}
%global a_var 1
%{warn %{is_enabled a_var OK NOT_OK}}'
warning: OK

v4.14.3:

$ rpm --eval '%define is_enabled() %{expr "%{%1}"=="1"?"%2":"%3"}
> %global a_var 1
> %{warn %{is_enabled a_var OK NOT_OK}}'
warning:
$


On Fri, 17 Jun 2022 at 18:27, Jason Vas Dias ***@***.***> wrote:

> Aargh !
>
> Why does this work with only RPM  v4.17 (Fedora 36), not with RPM v4.14.3
> (Rocky EL8) :
>
> with RPM v4.17:
> $ rpm --eval '%define is_enabled() %["%{expr %{%1}}"=="1"?"%2":"%3"]
> %global a_var 1
> %{warn:%{is_enabled a_var OK NOT_OK}}'
> warning: OK
> $
>
> with RPM v4.14.3:
> $ rpm --eval '%define is_enabled() %["%{expr %{%1}}"=="1"?"%2":"%3"]
> %global a_var 1
> %{warn %{is_enabled a_var OK NOT_OK}}'
> warning:
> $
>
>
> On Wed, 15 Jun 2022 at 18:44, Jason Vas Dias ***@***.***>
> wrote:
>
>> Best solution found :
>>
>> $ rpm --eval '%define is_enabled() %["%{expr
>> %{%1}}"=="1"?"Enabled":"Disabled"]
>> %global a_var 1
>> %{warn:%{is_enabled:a_var}}'
>> warning: Enabled
>> $
>>
>> Thanks Panu !
>>
>> But I'm still not quite getting why this breaks it:
>> rpm --eval '%define is_enabled()
>> %["%{expr:%{%1}}"=="1"?"Enabled":"Disabled"]
>>   ie. just adding the colon after expr             ^- here
>> makes rpm emit : "error: parse error in expression: %{a_var}".
>> Why ? I am calling all other macros with ':' (colons) separating macro
>> name from parameters -
>> why can't I do that with expr ?
>>
>> But anyway, problem solved ! Many thanks.
>>
>> On Tue, 14 Jun 2022 at 08:48, Panu Matilainen ***@***.***>
>> wrote:
>>
>>> Good question 👍
>>>
>>> A couple of fundamental problems there:
>>>
>>>    - function-like (aka parametric) macros, such as is_enabled() should
>>>    not be %global because with %global, the body is expanded at definition
>>>    time and any tests around eg %1 just melt away useless. Use %define
>>>    instead, and lot of weirdness goes away. Alternatively you can escape the
>>>    %1, but as a general guideline anything but simple constants, %define is
>>>    what you usually want. The "always use global" guidelines in various places
>>>    are misguided, really.
>>>    - the %{?%1} in is_enabled() tests whether that macro got an
>>>    argument or not, which is not what you want. Test with an expression
>>>    instead.
>>>
>>> For example:
>>>
>>> [pmatilai🎩︎localhost ~]$ rpm --eval '%["%{?a_var}"=="1"?"yes":"no"]'
>>>
>>> no
>>>
>>> [pmatilai🎩︎localhost ~]$ rpm --define "a_var 0" --eval '%["%{?a_var}"=="1"?"yes":"no"]'
>>>
>>> no
>>>
>>> [pmatilai🎩︎localhost ~]$ rpm --define "a_var 1" --eval '%["%{?a_var}"=="1"?"yes":"no"]'
>>>
>>> yes
>>>
>>>
>>> (Whether you use --eval or --define is a matter of style, but it's
>>> better to split stuff over multiple --define/--eval uses (they're simply
>>> processed in order), makes it easier to handle for us humans.)
>>>
>>> Turning that into a parametric macro gets you something like this:
>>>
>>> [pmatilai🎩︎localhost rpm]$ rpm --define '%is_enabled() %["%{?1}"=="1"?"yes":"no"]' --eval '%{is_enabled %a_var}'
>>>
>>> no
>>>
>>> [pmatilai🎩︎localhost rpm]$ rpm --define 'a_var 0' --define '%is_enabled() %["%{?1}"=="1"?"yes":"no"]' --eval '%{is_enabled %a_var}'
>>>
>>> no
>>>
>>> [pmatilai🎩︎localhost rpm]$ rpm --define 'a_var 1' --define '%is_enabled() %["%{?1}"=="1"?"yes":"no"]' --eval '%{is_enabled %a_var}'
>>>
>>> yes
>>>
>>>
>>> Note quoting around the %1 argument test: macros always expand to string
>>> values, so testing for integer value would only give you errors. The rest
>>> kinda depends what exactly you want to do with it.
>>>
>>> Hope that helps.
>>>
>>> —
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>>


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