CFLAGS
Encyclopedia
CFLAGS and CXXFLAGS are either the name of environment variable
s or of Makefile variables that can be set to specify additional switches to be passed to a compiler
in the process of building computer software
.
These variables are usually set inside a Makefile and are then appended to the command line when the compiler is invoked. If they are not specified in the Makefile, then they will be read from the environment, if present. Tools like autoconf
's ./configure script will usually pick them up from the environment and write them into the generated Makefiles.
CFLAGS allows to add switches for the C compiler, while CXXFLAGS is meant to be used when invoking a C++
compiler. Similarly, a variable CPPFLAGS exists with switches to be passed to the C preprocessor
.
These variables are most commonly used to specify optimization
or debugging
switches to a compiler, as for example
-specific)
Environment variable
Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer.They can be said in some sense to create the operating environment in which a process runs...
s or of Makefile variables that can be set to specify additional switches to be passed to a compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
in the process of building computer software
Computer software
Computer software, or just software, is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do it....
.
These variables are usually set inside a Makefile and are then appended to the command line when the compiler is invoked. If they are not specified in the Makefile, then they will be read from the environment, if present. Tools like autoconf
Autoconf
GNU Autoconf is a tool for producing configure scripts for building, installing and packaging software on computer systems where a Bourne shell is available....
's ./configure script will usually pick them up from the environment and write them into the generated Makefiles.
CFLAGS allows to add switches for the C compiler, while CXXFLAGS is meant to be used when invoking a C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
compiler. Similarly, a variable CPPFLAGS exists with switches to be passed to the C preprocessor
C preprocessor
The C preprocessor is the preprocessor for the C and C++ computer programming languages. The preprocessor handles directives for source file inclusion , macro definitions , and conditional inclusion ....
.
These variables are most commonly used to specify optimization
Optimization (computer science)
In computer science, program optimization or software optimization is the process of modifying a software system to make some aspect of it work more efficiently or use fewer resources...
or debugging
Debugging
Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware, thus making it behave as expected. Debugging tends to be harder when various subsystems are tightly coupled, as changes in one may cause bugs to emerge...
switches to a compiler, as for example
-g, -O2 or (GCCGNU Compiler Collection
The GNU Compiler Collection is a compiler system produced by the GNU Project supporting various programming languages. GCC is a key component of the GNU toolchain...
-specific)
-march=athlon.