- SIGSEGV
Infobox Computing signal
description = Invalid memory reference
action = Abnormal termination of the process
SEGV_MAPERR | Address not mapped to object
SEGV_ACCERR | Invalid permissions for mapped objectOnPOSIX -compliant platforms, SIGSEGV is the signal thrown bycomputer program s making invalid memory references, orsegmentation fault s. The symbolic constant for SIGSEGV is defined in theheader file signal.h. Symbolic signal names are used because signal numbers can vary across platforms; in practice it is usually signal #11.Etymology
"SIG" is a common prefix for signal names. "SEGV" is an
abbreviation of "segmentation violation".Usage
Computer programs may throw SIGSEGV for improper memory handling (see
segmentation fault ). Theoperating system may inform the application of the nature of the error using the signal stack, which developers can use todebug their programs or handle errors.The default action for a program upon receiving SIGSEGV is abnormal termination. This action will end the process, but may generate a
core file to aid debugging, or perform some other platform-dependent action. For example,Linux systems using thegrsecurity patch may log SIGSEGV signals in order to monitor for possible intrusion attempts usingbuffer overflow s.SIGSEGV can be caught; that is, applications can request what action they want to occur in place of the default. Examples of such action might be ignoring it, calling a function, or restoring the default action. In some circumstances, ignoring SIGSEGV results in
undefined behavior . [http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html] .An example of an application that might handle SIGSEGV is a
debugger , which might check the signal stack and inform the developer of what happened, and where the program terminated.SIGSEGV is usually generated by the
operating system , but users with appropriate permissions can use thekillsystem call or kill command (a userland program, or sometimes a shell builtin) to send the signal to a process at will.
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