gcc -E -dM/-dD

George2 · 10-14-2007, 02:06 AM

Hello everyone,

I am learning some other's code -- build files. Here are two samples which I am confused.

gcc -E -o ListDef -dM -P YourSrcCode.c

gcc -E -o ListDef -dD -P YourSrcCode.c

I have tried that in ListDef file (new generated after either of the two commands) and it contains several hundred lines of #define, typedef and some other definitions. Could anyone help to answer what is the function of the two commands? Differences between -dM and -dD?

thanks in advance,
George

reverse · 10-14-2007, 06:59 AM

`man gcc` explains all the options used.

You're welcome, in advance.

George2 · 10-14-2007, 09:25 AM

Thanks reverse,

Quote:

Originally Posted by reverse

`man gcc` explains all the options used.

You're welcome, in advance.

I have read the gcc PDF manual and also tried by myself. I can not fully understand in what situation do we need -dM and in what situation do we need -dD. Any experiences?

regards,
George

Alien_Hominid · 10-14-2007, 10:17 AM

dD - Dump all macro definitions, at the end of preprocessing, in addition to normal output.
dM - Dump after performing the machine dependent reorganization pass, to file.35.mach.

George2 · 10-15-2007, 09:37 AM

Thanks Alien_Hominid,

Quote:

Originally Posted by Alien_Hominid

dD - Dump all macro definitions, at the end of preprocessing, in addition to normal output.
dM - Dump after performing the machine dependent reorganization pass, to file.35.mach.

So, using -dM is more accurate to real preprocessor work? (since you mentioned it also performed machine dependent reorganization pass)?

regards,
George

Alien_Hominid · 10-15-2007, 02:31 PM

Those are used only for debugging the compiler.