[bug #23128] Non-reentrant library calls should be made reentrant

[avrs-admin]

Thu 01 May 2008 04:45:56 PM CEST

The avr-libc FAQ has a more detailed discussion on non-reentrant library calls.  (See patch #6500 if the reentrant update to the FAQ has not yet been applied.)

This bug has been opened as a placeholder for those calls which could be made reentrant.  It is low priority since reasonable workarounds exist.

Short duration calls and macros that appear in the FAQ that can easily be reentrant with a cli()/sei() or ATOMIC_BLOCK() are not included in this bug.

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Calls:        strtod(), strtol(), strtoul()

Issue:        They all use the global "errno".  Errno could be returned wrong.

Possible fix: Create *_r versions, similar to strtok_r(), where the error status is returned via a passed pointer to an int or uint8_t.

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Calls:        printf(), vprintf(), puts()

Issue:        stdout is global and these calls alter a character counter in stdout's FILE struct via vfprintf().  Returned character count could be wrong.

Possible fix: Instead of changing values in stdout, perhaps introduce another call layer like vfprintf_r(), so that character count can be kept on the stack.

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Calls:        printf_P(), vprintf_P(), puts_P()

Issue:        stdout is global and in addition to the character count issue above, these calls also alter a flag in stdout to make vfprintf() read format strings from PGM space.

Possible fix: Similar to above.  A call layer to keep the keep the flag values on the stack could work.

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Calls:        fprintf(), fprintf_P(), vfprintf(), vfprintf_P(), fputs(), fputs_P()

Issue:        The same problems exist as with stdout above when using a global FILE with these calls.

Possible fix: Same as printf().

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Calls:        assert()

Issue:        Uses fprintf().

Possible fix: Fixed when fprintf() is fixed.

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Calls:        getchar(), gets()

Issue:        stdin is global and these calls alter flags, character count, and the unget buffer in stdin's FILE struct.

Possible fix: None?  Needs locking because unget buffer is persistent between calls and locking is implementation dependent.  Could create *_r versions and have a non-global unget but it may not be worth the trouble.

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Calls:        fgetc(), ungetc(), fgets(), scanf(), scanf_P(), fscanf(), fscanf_P(), vscanf(), vfscanf(), vfscanf_P(), fread()

Issue:        The same problems exist as with stdin above when using a global FILE with these calls.

Possible fix: None?  See above for getchar().

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This issue was migrated from https://savannah.nongnu.org/bugs/?23128