Signal-Handling Functions

Choosing Signal Support Using oesigsetup

The oesigsetup function enables you to control which signals are managed by USS and which use support internal to the SAS/C library. oesigsetup must be called before any other signal-related function.

If there is no call to oesigsetup in a program called with exec linkage, the library assumes that all signals should be managed by USS, if possible. If there is no call to oesigsetup in a program not called with exec linkage (a regular batch or TSO execution), the library assumes that no signals should be managed by USS.

Note: This means that you must call oesigsetup in a program without exec linkage if you need to use USS signals. [cautionend]

The arguments to oesigsetup are two signal sets. The first defines the set of signals to be managed by USS, and the second defines the signals to be managed by SAS/C. oesigsetup fails if any signal is included in both sets; unspecified signals are handled as if oesigsetup had not been called.

Error Signals with Flexible Handling

The signals with flexible handling can be divided into two groups: error signals and other signals. The error signals, normally associated with program error condition, are SIGABND , SIGABRT , SIGFPE, SIGILL , and SIGSEGV . If these signals are handled as SAS/C conditions, USS is not informed of the error when the corresponding error condition occurs. If the error leads to termination, USS sets the final status of the terminated process to terminated by SIGKILL rather than a more specific status; otherwise, you can expect no undesirable effects.

Note: Starting with Release 6.00 of SAS/C software, the SIGABND signal is used to indicate a system ABEND. As described in the next section, this is a behavior change from previous versions of SAS/C. [cautionend]

Non-Error Signals with Flexible Handling

The non-error signals with flexible handling are SIGALRM , SIGINT , SIGIO , SIGTERM , SIGUSR1 , and SIGUSR2 . If USS handles SIGALRM , the SAS/C extension functions alarmd and sleepd are not available. If the SAS/C library handles SIGALRM , the ps shell command does not accurately indicate when the process is sleeping.

If SAS/C handles SIGINT , SIGINT is generated by use of the TSO attention key for a program running under TSO. If USS handles SIGINT , SAS/C does not use the STAX macro or attempt to handle TSO attentions. Be aware that SAS/C handling of SIGINT is not useful in non-TSO address spaces.

SIGIO has no special meaning at present to either USS or SAS/C but might be used by future versions of either product.

SIGTERM has no defined meaning to SAS/C and, therefore, can be generated only by use of the raise function if managed by SAS/C.

SIGUSR1 and SIGUSR2 have no special meaning to USS. If oesigsetup defines these signals as managed by SAS/C, then you can use SAS/C user-added signal support to define a meaning for one of these symbols.

Note: If you have defined a signal as handled by SAS/C and the signal is generated by USS, the result is always the USS default action for the signal. For example, if you define SIGTERM as a SAS/C signal and establish a handler, after which another process uses the kill function to send your process a SIGTERM signal, your handler will not be called and the process will be terminated. [cautionend]

A program can use kill to send a signal that oesigsetup has defined as a signal managed by SAS/C. If a program sends the signal to itself, only default handling will take place.

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