구차니의 잡동사니 모음

-D name

Predefine name as a macro, with definition 1. 

-D name=definition

The contents of definition are tokenized and processed as if they appeared during translation phase three in a ‘#define’ directive. In particular, the definition will be truncated by embedded newline characters.

If you are invoking the preprocessor from a shell or shell-like program you may need to use the shell's quoting syntax to protect characters such as spaces that have a meaning in the shell syntax.

If you wish to define a function-like macro on the command line, write its argument list with surrounding parentheses before the equals sign (if any). Parentheses are meaningful to most shells, so you will need to quote the option. With sh and csh, -D'name(args...)=definition' works.

-D and -U options are processed in the order they are given on the command line. All -imacros file and -include file options are processed after all -D and -U options. 

-U name

Cancel any previous definition of name, either built in or provided with a -D option. 

-undef

Do not predefine any system-specific or GCC-specific macros. The standard predefined macros remain defined. 

[링크 : https://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html] 

$ cat test.c

#include <stdio.h>

#include <setjmp.h>

jmp_buf pos;

void proc()

{

   static int i = 0;

   ++i;

   if(i<10)

       longjmp(pos, i);

   return;

}

int main()

{

   int a;

   a = setjmp(pos);

   printf("%d\n", a);

   proc();

   return 0;

}

[링크 : http://www.jiniya.net/wp/archives/5030]

[링크 : http://egloos.zum.com/studyfoss/v/5275830]

#include <setjmp.h>

int setjmp(jmp_buf env);

void longjmp(jmp_buf env, int val);

[링크 : http://linux.die.net/man/3/setjmp]

[링크 : http://linux.die.net/man/3/longjmp] 

$ vi auto.c

void add_ints(int * __restrict pa, int * __restrict pb, unsigned int n, int x)

{

    unsigned int i;

    for(i = 0; i < (n & ~3); i++)

        pa[i] = pb[i] + x;

}

$ arm-linux-gnueabihf-gcc -mfpu=neon -ftree-vectorize -c auto.c

$ arm-linux-gnueabihf-objdump -D auto.o

[링크 : http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dht0002a/ch01s04s03.html] 

-mfpu=name

This specifies what floating-point hardware (or hardware emulation) is available on the target. Permissible names are: ‘vfp’, ‘vfpv3’, ‘vfpv3-fp16’, ‘vfpv3-d16’, ‘vfpv3-d16-fp16’, ‘vfpv3xd’, ‘vfpv3xd-fp16’, ‘neon’, ‘neon-fp16’, ‘vfpv4’, ‘vfpv4-d16’, ‘fpv4-sp-d16’, ‘neon-vfpv4’, ‘fpv5-d16’, ‘fpv5-sp-d16’, ‘fp-armv8’, ‘neon-fp-armv8’, and ‘crypto-neon-fp-armv8’.

If -msoft-float is specified this specifies the format of floating-point values.

If the selected floating-point hardware includes the NEON extension (e.g. -mfpu=‘neon’), note that floating-point operations are not generated by GCC's auto-vectorization pass unless -funsafe-math-optimizations is also specified. This is because NEON hardware does not fully implement the IEEE 754 standard for floating-point arithmetic (in particular denormal values are treated as zero), so the use of NEON instructions may lead to a loss of precision. 

[링크 : https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html]

    [링크 : https://www.raspberrypi.org/forums/viewtopic.php?f=33&t=98354]