GNU Compiler (GCC)
GCC Syntax
#gcc [options] [source files] [object files] [-o output file]
GCC Options
options
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description
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-c
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compile source files to object files without linking. Generate object file
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-Dname[=value]
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define a preprocessor macro
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-fPIC
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generate position independent code (PIC) for shared libraries
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-fpic
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generate more efficient code (than -fPIC), if supported by the platform compiler
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-glevel
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generate debug information to be used by GDB
-g0: no debug information
-g1: minimal debug information
-g : default debug information
-g3: maximal debug information
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-Idir
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add include directory of header files
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-llibname
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link with library file (library name without the lib prefix and the .a or .so extensions). Default link shared library (.so), '-static' to link static library
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-Ldir
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look in directory for library files
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-o output_file
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write build output to output file
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-Olevel
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set the compiler's optimization level for code size and execution time.
'optimization level' described in table below.
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-shared
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generate shared object file for shared library
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-Uname
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undefine a preprocessor macro
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-w
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disable all warning messages
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-Wall
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enable all compiler's warning messages
NOTE: This option should always be used, in order to generate better code.
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-Wextra
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enable extra warning messages
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-g
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Generate debugging information
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-fpic -shared
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No text relocations for shared libraries
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-Werror=format-security
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Reject potentially unsafe format string arguments
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-Werror=implicit-function-declaration
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Reject missing function prototypes
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Recommened to use
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options
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optimization level
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execution time
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code size
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memory usage
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compile time
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-O0
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optimization for compilation time (Default)
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+
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+
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-
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-
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-O1 / -O
|
optimization for code size and execution time
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-
|
-
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+
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+
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-O2
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optimization more for code size and execution time
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--
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x
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+
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++
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-O3
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optimization more for code size and execution time
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---
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x
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+
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+++
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-Os
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optimization for code size
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x
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--
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x
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++
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-Ofast
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O3 with fast none accurate math calculations
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---
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x
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+
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+++
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+increase , ++increase more, +++increase even more, -reduce, --reduce more, ---reduce even more, x No change
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