SAS/C Software: Changes and Enhancements, Release 6.50

Enhanced OpenEdition Library Functions

This section describes the SAS/C OpenEdition library functions enhanced by Release 6.50.

alarmd

As a result of changes in the MVS operating system, the alarmd function description for Release 6.50 requires an update in the CAUTION Section of the "Function Descriptions" in Chapter 6 of the SAS/C Library Reference, Volume 1, Release 6.00 on page 6-32.

Replace the following sentence under CAUTION:

Old If SIGALRM is handled by OpenEdition, alarmd is not available.

New If SIGALRM is handled by OpenEdition, alarmd is not available in releases of MVS prior to MVS 5.2.2.

siglongjmp and blkjmp

The sigsetjmp and siglongjmp functions, introduced in SAS/C Release 6.00, allow the signal mask to be saved as part of a setjmp operation, and restored as part of a longjmp operation. In the 6.00 implementation, siglongjmp restored the signal mask before searching the stack for blkjmp callers.

This meant that the old signal mask was restored before any caller of blkjmp received control to intercept the jump. Since in most cases the restored signal mask allows more signals than the old signal mask, this had the effect of allowing a signal to be discovered in a blkjmp cleanup routine, thereby causing part of the cleanup to be bypassed.

The 6.50 version of the library modifies siglongjmp so that the signal mask is changed as late as possible. If there is no interference from blkjmp callers, the signal mask is changed immediately before control is returned to the target sigsetjmp call.

As with the 6.00 library, if a call to siglongjmp is intercepted by blkjmp, the signal mask is restored immediately before control is returned to the blkjmp call.

Additionally, a new function called sigblkjmp has been defined. This function is an enhanced version of blkjmp, which stores the signal mask data associated with a siglongjmp in the buffer passed to sigblkjmp as well as the registers and other environmental information.

This means that the signal mask is not changed when control is given to a sigblkjmp cleanup routine. The mask is only changed when control passes to the original sigsetjmp call, or to a caller of the old blkjmp function.

Use of sigblkjmp rather than blkjmp is recommended in any program which uses sigsetjmp and siglongjmp.

Note: Both blkjmp and sigblkjmp are compatible with both the setjmp and longjmp functions as well as with their sig- versions. [cautend]

sleepd

As a result of changes in the MVS operating system, the sleepd function description requires an update in the DESCRIPTION Section of the "Function Descriptions" in Chapter 6 of the SAS/C Library Reference, Volume 1, Release 6.00 on page 6-434.

Replace the following sentences under DESCRIPTION:

Old If SIGALRM is managed by OpenEdition, the sleep function is implemented by OpenEdition, and the sleepd function is not implemented. In this case, note that the occurrence of a signal managed by SAS/C does not cause sleep to terminate.

New If SIGALRM is managed by OpenEdition, the sleep and sleepd functions are implemented by OpenEdition. In this case, note that the occurrence of a signal managed by SAS/C does not cause sleep or sleepd to terminate.

tcsetpgrp

IBM has changed the way the OpenEdition tcsetpgrp system call works. As a result, several changes for Release 6.50 are required to the existing documentation, SAS/C Library Reference, Volume 2, Release 6.00.

First, the tcsetpgrp function needs an addition note in the DESCRIPTION Section on page 20-96 to clarify the process handling of the SIGTTOU signal.

Replace the following sentence under DESCRIPTION:

Old Note not required.

New
Note: If tcsetpgrp is called from a background process, the signal SIGTTOU is generated, unless the signal is ignored or blocked. If the signal is defaulted, this will cause the calling process to stop. If the signal is handled, tcsetpgrp will set errno to EINTR and fail. For this reason, you should ignore or block SIGTTOU if you call tcsetpgrp from a background process. [cautend]

Second, a minor typographical error was discovered in last paragraph of the tcsetpgrp DESCRIPTION Section on page 20-96 and was not corrected by the errata sheet for Volume 2.

Make the following correction under DESCRIPTION:

Old SITTIN

New SIGTTIN

Lastly, due to its level of complexity, the example for setpgid, which uses tcsetpgrp, requires modifications. The setpgid example is located in the SAS/C Library Reference, Volume 2, Release 6.00 in the middle of page 20-75.

Replace the following lines under EXAMPLE:

Old

/* become foreground process group */
if (tcsetpgrp(STDIN_FILENO, getpid()))
     erreport("tcsetpgrp");

New

/* ignore SIGTTOU during tcsetpgrp */
signal(SIGTTOU, SIG_IGN);
/* become foreground process group */
if (tcsetpgrp(STDIN_FILENO, getpid()))
      erreport("tcsetpgrp");
/* restore normal SIGTTOU handling */
signal(SIGTTOU, SIG_DFL);

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Old	If `SIGALRM` is handled by OpenEdition, `alarmd` is not available.
New	If `SIGALRM` is handled by OpenEdition, `alarmd` is not available in releases of MVS prior to MVS 5.2.2.

Old	If `SIGALRM` is managed by OpenEdition, the `sleep` function is implemented by OpenEdition, and the `sleepd` function is not implemented. In this case, note that the occurrence of a signal managed by SAS/C does not cause `sleep` to terminate.
New	If `SIGALRM` is managed by OpenEdition, the `sleep` and `sleepd` functions are implemented by OpenEdition. In this case, note that the occurrence of a signal managed by SAS/C does not cause `sleep` or `sleepd` to terminate.

Old	Note not required.
New	Note: If `tcsetpgrp` is called from a background process, the signal `SIGTTOU` is generated, unless the signal is ignored or blocked. If the signal is defaulted, this will cause the calling process to stop. If the signal is handled, `tcsetpgrp` will set `errno` to `EINTR` and fail. For this reason, you should ignore or block `SIGTTOU` if you call `tcsetpgrp` from a background process.