On 06.04.26 23:31, Tom Lane wrote:
Peter Eisentraut <[email protected]> writes:
I have committed this patch set. I also added a test into the C++ module.
BF member ayu is failing said test:
ccache clang++-4.0 -std=gnu++11 -Wall -Wpointer-arith -Werror=vla
-Wmissing-format-attribute -Wimplicit-fallthrough -Wformat-security
-fno-strict-aliasing -fwrapv -g -O2 -fPIC -fvisibility=hidden
-fvisibility-inlines-hidden -I. -I. -I../../../../src/include -D_GNU_SOURCE
-I/usr/include/libxml2 -c -o test_cplusplusext.o test_cplusplusext.cpp
test_cplusplusext.cpp:66:3: warning: unannotated fall-through between switch
labels [-Wimplicit-fallthrough]
case 2:
^
test_cplusplusext.cpp:66:3: note: insert '[[clang::fallthrough]];' to silence
this warning
case 2:
^
[[clang::fallthrough]];
test_cplusplusext.cpp:66:3: note: insert 'break;' to avoid fall-through
case 2:
^
break;
1 warning generated.
I don't know if it's worth catering to this extremely old
clang version ...
It appears that we could satisfy clang 6 through 9 with something like
#elif defined(__clang__)
#define pg_fallthrough [[clang::fallthrough]]
#else
Clang >=10 support the existing #elif __has_attribute(fallthrough) branch.
But AFAICT, clang 5 and older are completely broken in this regard,
because they react to the presence of [[clang::fallthrough]] with a
syntax error ("error: expected expression"). Not even clang's own
example code[0] works.
[0]:
https://releases.llvm.org/5.0.2/tools/clang/docs/AttributeReference.html#fallthrough-clang-fallthrough
Also, this only appears to affect C++. In C mode, before clang 10, the
warning option -Wimplicit-fallthrough doesn't appear to do anything.
