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* [Bug c/67266] New: Use of "cpp -P ..." collapses multiple blank lines @ 2015-08-19 0:43 mike at flyn dot org 2015-08-19 1:27 ` [Bug preprocessor/67266] " pinskia at gcc dot gnu.org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: mike at flyn dot org @ 2015-08-19 0:43 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67266 Bug ID: 67266 Summary: Use of "cpp -P ..." collapses multiple blank lines Product: gcc Version: 5.1.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: mike at flyn dot org Target Milestone: --- I am using: cpp -C -P -nostdinc -std=c99 -Werror to process something that is not C. Everything works, except that one side effect of "-P" is that consecutive newlines are compressed into one. For example, $ cpp -P x x outputs x x I have not found documentation of this behavior. My hunch is that -P should not behave this way because the man page states, "this might be useful when running the preprocessor on something that is not C code." I would think that users employing cpp to process non-C would expect newlines to be preserved. I previously brought this up on the GCC mailing list. See https://gcc.gnu.org/ml/gcc-help/2015-08/msg00069.html. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug preprocessor/67266] Use of "cpp -P ..." collapses multiple blank lines 2015-08-19 0:43 [Bug c/67266] New: Use of "cpp -P ..." collapses multiple blank lines mike at flyn dot org @ 2015-08-19 1:27 ` pinskia at gcc dot gnu.org 2015-08-19 1:46 ` mike at flyn dot org 2015-08-19 2:08 ` msebor at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2015-08-19 1:27 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67266 --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- From https://gcc.gnu.org/onlinedocs/gcc-5.2.0/cpp/Preprocessor-Output.html#Preprocessor-Output : The output from the C preprocessor looks much like the input, except that all preprocessing directive lines have been replaced with blank lines and all comments with spaces. Long runs of blank lines are discarded. -P does not change that. You might want to look into using -tranditional-cpp also because if you are using preprocessor for other than C, # might be treated not like what you want it to be treated ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug preprocessor/67266] Use of "cpp -P ..." collapses multiple blank lines 2015-08-19 0:43 [Bug c/67266] New: Use of "cpp -P ..." collapses multiple blank lines mike at flyn dot org 2015-08-19 1:27 ` [Bug preprocessor/67266] " pinskia at gcc dot gnu.org @ 2015-08-19 1:46 ` mike at flyn dot org 2015-08-19 2:08 ` msebor at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: mike at flyn dot org @ 2015-08-19 1:46 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67266 --- Comment #2 from W. Michael Petullo <mike at flyn dot org> --- This does not seem to be the behavior of cpp without the -P flag: $ cpp x x outputs # 1 "<stdin>" # 1 "<built-in>" # 1 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 1 "<command-line>" 2 # 1 "<stdin>" x x Here cpp does not collapse the newline. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug preprocessor/67266] Use of "cpp -P ..." collapses multiple blank lines 2015-08-19 0:43 [Bug c/67266] New: Use of "cpp -P ..." collapses multiple blank lines mike at flyn dot org 2015-08-19 1:27 ` [Bug preprocessor/67266] " pinskia at gcc dot gnu.org 2015-08-19 1:46 ` mike at flyn dot org @ 2015-08-19 2:08 ` msebor at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: msebor at gcc dot gnu.org @ 2015-08-19 2:08 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67266 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |msebor at gcc dot gnu.org --- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> --- The "long runs of blank lines are discarded" part refers to the constant 8 hardcoded in the maybe_print_line_1 function. The constant's effect can be seen in the following test case. The first sequence of 7 newlines is retained while the second one of 8 newlines is compressed. $ cat -n a.txt && gcc -dU -E -xc a.txt | cat -n 1 line 1 2 3 4 5 6 7 8 line 8 9 10 11 12 13 14 15 16 17 line 17 1 # 1 "a.txt" 2 # 1 "<built-in>" 3 # 1 "<command-line>" 4 # 1 "/usr/include/stdc-predef.h" 1 3 4 5 #undef _STDC_PREDEF_H 6 #define __GCC_IEC_559 2 7 #define __GCC_IEC_559_COMPLEX 2 8 # 1 "<command-line>" 2 9 # 1 "a.txt" 10 line 1 11 12 13 14 15 16 17 line 8 18 # 17 "a.txt" 19 line 17 ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2015-08-19 2:08 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-08-19 0:43 [Bug c/67266] New: Use of "cpp -P ..." collapses multiple blank lines mike at flyn dot org 2015-08-19 1:27 ` [Bug preprocessor/67266] " pinskia at gcc dot gnu.org 2015-08-19 1:46 ` mike at flyn dot org 2015-08-19 2:08 ` msebor at gcc dot gnu.org
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