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Help text for ld magic number options

Fangrui Song i@maskray.me
Mon Feb 24 00:04:00 GMT 2020 
On 2020-02-22, Stephen Casner wrote:
>Thanks, Alan, for addressing bug 25569 more thoroughly than I would be
>able to do.
>
>To all, next I have three proposed changes related to the magic number
>options for ld on which I solicit your feedback.  First a simple one.
>
>The output of ld --help includes the following:
>
>  -n, --nmagic     Do not page align data
>  -N, --omagic     Do not page align data, do not make text readonly
>  --no-omagic      Page align data, make text readonly
>
>The help text for --nmagic is not accurate for the pdp11-aout target
>and I believe not for others as well.  That option results in setting
>config.text_read_only = TRUE, and in order to make the text read-only
>the data must be aligned to a separate page on the PDP11 and I presume
>for most if not all other computers as well.
>
>The references to page alignment really correspond to the setting of
>config.magic_demand_paged which, when TRUE, selects the ZMAGIC (0413)
>format in aoutx.h.  That format does require the data to be page
>aligned, but more significantly it indicates to the runtime system to
>do demand paging.  The pdp11-aout code in bfd/pdp11.c does not
>implement the ZMAGIC format (even though there is some stub code for
>it included when copying from aoutx.h) since demand paging isn't
>practical on the PDP11 and wasn't implemented for it over the full
>timespan from Unix v6 through 2.11 BSD.  Thus, for pdp11-aout the
>options --no-omagic and --nmagic produce the same result.
>
>I propose that the help text be changed as follows:
>
>  -n, --nmagic     Make text readonly, page align data, no demand paging
>  -N, --omagic     Do not make text readonly, do not page align data
>  --no-omagic      Make text readonly, page align data, do demand paging
>
>Is that acceptable?  This would have implications for the ld
>documentation as well.
>

http://man.cat-v.org/unix_10th/5/a.out

           #define  OMAGIC    0407       /* old impure format */
           #define  NMAGIC    0410       /* read-only text */
           #define  ZMAGIC    0413       /* demand load format */

>  -n, --nmagic     Make text readonly, page align data, no demand paging

Should something else be changed, rather than change --nmagic to behave
differently from other architectures?

(Why isn't --no-omagic named --zmagic ? :)
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