[Bug 245006] toolchain: clang issues bogus "warning: multi-line // comment [-Wcomment]"
bugzilla-noreply at freebsd.org
bugzilla-noreply at freebsd.org
Mon Mar 23 13:29:30 UTC 2020
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=245006
Bug ID: 245006
Summary: toolchain: clang issues bogus "warning: multi-line //
comment [-Wcomment]"
Product: Base System
Version: 12.1-RELEASE
Hardware: Any
URL: https://github.com/Genivia/RE-flex/issues/68
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: standards
Assignee: standards at FreeBSD.org
Reporter: mandree at FreeBSD.org
CC: toolchain at FreeBSD.org
Greetings,
debugging a ports/textproc/re-flex 1.6.4 issue, I came across a standards
violation in clang, observed in base clang 8.0.1 (FreeBSD 12.1 amd64), ports
clang 9 and clang-devel as of today (llvm90-9.0.1 llvm-devel-11.0.d20200117),
but not gcc-9.2.0 from ports.
Save these two lines as try.c:
// \
x
void f(void) {}
Then observe:
$ gcc -pedantic-errors -std=c11 -c /tmp/try.c
(no output)
$ /usr/bin/clang -pedantic-errors -std=c11 -c /tmp/try.c
/tmp/try.c:1:4: error: multi-line // comment [-Werror,-Wcomment]
// \
^
1 error generated.
Reading up in C99, C11, C++11, it is clear that line merging happens in
compilation phase 2, before phase 3 elides comments and replaces them by one
space.
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