Intel C/C++ compiler flags for runtime checks
The icc/icpc compilers can instrument code to do a number of runtime checks. This will have a performance impact, so production code should never be compiled with these options enabled.
Floating point exceptions
The compiler can instrument the code to trap floating point exceptions. The fp-trap (in main) and -fp-trap-all (in all functions) options take the following values as a comma-separated list:
invalid,divzero,overflow,common: the previous three values,denormal,underflow,inexact: probably not very useful since most floating point operations will lead to loss of accuracy,all.
It may also be helpful to switch on floating point stack checking after each function call, which you can do by adding the -fp-stack-check flag.
To instrument for the most common floating point exceptions, compile with:
$ icc -fp-trap-all=common -fp-stack-check ...
Bounds & pointer checks
Getting an array index wrong is easy, and trying to access an array using an index that is out of bounds usually results in a crash of your application with a segmentation fault (or not, which is most likely worse).
The compiler can insert code into your application to check array bounds at runtime. When you run an application that has been compiled using this option, your application will still crash, but with an informative error message.
$ icc -check-pointers=rw ...
In the example above, both read and write access through pointers is checked at runtime. To limit checks to writes only, specify write rather than rw.
Note: this compiler option should only be used for development and testing, not for production. A performance penalty is incurred since extra instructions have to be executed when your application runs.
Additionally, the compiler can also generate code to check whether dangling pointers are used, i.e., pointers to memory that has already been deallocated.
$ icc -check-pointers=rw -check-pointers-dangling=all ...
To check for stack buffer overruns, the icc/icpc compilers provide a specific flags as well. The -fstack-protector enables overrun checks on some types of buffers, while -fstack-protector-strong will check for all types of buffers. Additionally, the -fstack-protector-all flag will ensure checks in all functions.
$ icpc -fstack-protector-strong -fstack-protector-all ...
Alternatively, the options -check=stack can also be used to detect stack buffer overruns and underruns.
Uninitialised variables
It is good practice to explicitly initialise variables. In many circumstances, forgetting to initialise a variable can lead to interesting and random results. The compiler can instrument the code to check for uninitialised variables at runtime. When such a variable is used, your application will crash with an appropriate informative error message.
$ icc -check=uninit ...
Note: this compiler option should only be used for development and testing, not for production. A performance penalty is incurred since extra instructions have to be executed when your application runs.
Note: when the compiler flag -Wremarks is used, the compiler will also generate warnings on potentially uninitialised variables.
Other checks
To check for narrowing conversions at runtime, the -check=conversions option is useful.