Pointer arguments to functions that are input only should be declared "const"

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Marking the pointer parameter as "const", particularly for string arguments, allows them to be called using string literals or other data that is already constant.

This may make a substantial difference on some targets where the executable can actually be linked to put the read-only data section in ROM rather than RAM. However, in order to do this properly/safely the code must treat this as read-only data. By declaring it "const" the compiler will flag any writes to it.

Changing the prototypes should not affect current usage.

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Imported from trac issue 28. Created by jphickey on 2015-01-22T09:48:19, last modified: 2019-03-05T14:57:55

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Trac comment by jphickey on 2015-01-26 16:24:11:

Branch "trac-28-const_pointer_args" pushed -- commit [changeset:bed05ea]

This adds a "const" designation to the function prototypes where applicable. This set may not be 100% complete, but it gets all the low hanging fruit.

This changeset also rolls in the fix for #40 and #52

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Trac comment by jphickey on 2015-03-13 16:02:06:

DEPENDENCY NOTE: using this change set also requires taking PSP trac 15:

[https://babelfish.arc.nasa.gov/trac/cfs_psp/ticket/15]

This fixes the PSP calls to adhere to the modified prototypes on the CFE side.

There is also a separate merge commit [changeset:2bd5438] that is also required when merging this with the fix for trac #32. These are pushed separately since there has not been a new baseline (yet) that already includes trac 1.

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Trac comment by jphickey on 2015-04-06 11:51:56:

This is ready for review/merge

The merge changeset for the two parts of this fix can be viewed in [changeset:29c1ec9].

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Trac comment by sstrege on 2015-04-06 13:18:55:

Concur with changes involving the addition of the "const" keyword.

The diff did show some other changes that are unrelated to this ticket:

cfe_time_utils.h - copyright character changed?

cfe_tbl_task_cmds.c - changed PSP_MemCpy to strncpy - I'm OK with this change

es_UT.c - removed typecast from function prototypes?

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Trac comment by jphickey on 2015-04-06 13:59:26:

My comments to the comments:

• cfe_time_utils.h copyright character - This was unintentional and appears to be due to Eclipse "fixing" encoding issues with utf-8, as the original was neither utf-8 nor ascii. Warrants another discussion on whether we should make all files UTF-8 or stick to straight ASCII? If the latter, we need to remove all special characters and replace it with e.g. (c). But this is a separate issue. I can revert this back using a different tool but this will be invalid utf-8 again.

• es_UT.c - After fixing the prototypes, the typecasting on these calls becomes unnecessary and actually wrong - the compiler would complain about a type mismatch here //due to// the typecast. Now the simple way is also the right way.

• cfe_tbl_task_cmds.c - This change also got inadvertently pulled into this change set. (FYI I am backporting/isolating all these changes from my other work tree). I can put this in a separate ticket if desired - let me know!

However, the change from memcpy() to strncpy() is absolutely necessary here - the former will read past the end of the source string if it is less than CFE_TBL_MAX_FULL_NAME_LEN characters.

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Trac comment by acudmore on 2015-04-07 12:38:18:

Concur.

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Trac comment by glimes on 2015-04-07 13:02:50:

Tested changesets [changeset:bed05ea51] [changeset:29c1ec922] as part of the ic-2015-03-10 merge.

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Trac comment by glimes on 2015-04-13 15:14:21:

Part of integration candidate 2015-03-10,
committed to cFS CFE Development branch on 2015-04-10
as part of merge [changeset:7d6f6d0].

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Trac comment by glimes on 2016-02-16 13:16:45:

Susie confirmed these tickets have been approved for CFE 6.5

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Trac comment by jhageman on 2019-03-05 14:57:55:

Milestone renamed