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[Bug preprocessor/41540] -dM -E doesn't #define __FILE__
- From: "msebor at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 2 Oct 2009 18:00:55 -0000
- Subject: [Bug preprocessor/41540] -dM -E doesn't #define __FILE__
- References: <bug-41540-1186@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from msebor at gmail dot com 2009-10-02 18:00 -------
I understand that the values of __FILE__ and __LINE__ change within the same
translation unit and thus may not be meaningful in the output of -dM -E. But
the values of __DATE__ and __TIME__ do not change within a translation unit
and so they could and IMO should be included in the output.
In any case, since the preprocessed output contains all the standard macros
expanded, I think it's reasonable to either see them all in the output of
-dM -E or the discrepancies between the two kinds of output to be mentioned
in the docs. I don't insist on including an exhaustive list of all macros
excluded from the output if this list is large or changes depending on
compiler options etc. but I do think that the docs ought to be clarified
so as not to state that *all* macros are output.
Here's a small test program to show the discrepancies:
$ cat u.c && gcc -E u.c && gcc -E -dM u.c | grep -e__DATE__ -e__FILE__
-e__LINE__ -e__STDC__ -e__STDC_HOSTED__ -e__STDC_VERSION__ -e__TIME__
char date[] = __DATE__;
int line = __LINE__;
char file[] = __FILE__;
char time[] = __TIME__;
int stdc = __STDC__;
int stdc_hosted = __STDC_HOSTED__;
# 1 "u.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "u.c"
char date[] = "Oct 2 2009";
int line = 2;
char file[] = "u.c";
char time[] = "11:52:51";
int stdc = 1;
int stdc_hosted = 1;
#define __STDC_HOSTED__ 1
#define __STDC__ 1
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41540