13.4 Runtime error messages

error while loading shared libraries:

cannot open shared object file: No such file or directory

The program uses shared libraries, but the necessary shared library files cannot be found by the dynamic linker when the program starts. The search path for shared libraries is controlled by the environment variable LD_LIBRARY_PATH (see section 3.2 Shared libraries and static libraries).

Segmentation fault

Bus error

These runtime messages indicate a memory access error. Common causes include:

• dereferencing a null pointer or uninitialized pointer
• out-of-bounds array access
• incorrect use of malloc, free and related functions
• use of scanf with invalid arguments

There is a subtle difference between segmentation faults and bus errors. A segmentation fault occurs when a process tries to access memory protected by the operating system. A bus error occurs when valid memory is accessed in an incorrect way (for example, trying to read an unaligned value on architectures where values must be aligned with 4-byte offsets).

floating point exception

This runtime error is caused by an arithmetic exception, such as division by zero, overflow, underflow or an invalid operation (e.g. taking the square root of -1). The operating system determines which conditions produce this error. On GNU systems, the functions feenableexcept and fedisableexcept can be used to trap or mask each type of exception.

Illegal instruction

This error is produced by the operating system when an illegal machine instruction is encountered. It occurs when code has been compiled for one specific architecture and run on another.