On Wed, Apr 06, 2016 at 09:50:48AM +0100, Jonathan Wakely wrote:
On 06/04/16 09:39 +0200, Eric Botcazou wrote:
>we recently ran into build failures on Windows systems using a somewhat old
>grep, coming from a syntax error in the libstdc++-symbols.ver version file:
>
># Symbol versioning for shared libraries.
>if ENABLE_SYMVERS
>libstdc++-symbols.ver: ${glibcxx_srcdir}/$(SYMVER_FILE) \
> $(port_specific_symbol_files)
> cp ${glibcxx_srcdir}/$(SYMVER_FILE) $@.tmp
> chmod +w $@.tmp
> if test "x$(port_specific_symbol_files)" != x; then \
> if grep '^# Appended to version file.' \
> $(port_specific_symbol_files) /dev/null > /dev/null 2>&1; then
>\
> cat $(port_specific_symbol_files) >> $@.tmp; \
> else \
> sed -n '1,/DO NOT DELETE/p' $@.tmp > tmp.top; \
> sed -n '/DO NOT DELETE/,$$p' $@.tmp > tmp.bottom; \
> cat tmp.top $(port_specific_symbol_files) tmp.bottom > $@.tmp; \
> rm tmp.top tmp.bottom; \
> fi; \
> fi
>
>Note the double /dev/null on the grep command line. The first one causes the
>grep to fail when the command is invoked on these systems. That's old code,
>but it is now invoked for config/abi/pre/float128.ver on the mainline and 5
>branch and this breaks the build on these systems (4.9 builds fine).
>
>This first /dev/null doesn't serve any useful purpose and seems to be a typo,
Doesn't it mean that if $port_specific_symbol_files contains only
whitespace we don't hang waiting for input from stdin? The 'if' above
it will be true when "x$port_specific_symbol_files" = "x " or similar.
I don't see any way for that to happen in the FSF tree, so it should
be safe. I'm a bit concerned about making that change this late in
stage 4 though. There isn't much time to find out if it breaks an
obscure target.
As it is a make variable, can't make be used to test this?
So perhaps
chmod +w $@.tmp
ifneq ($(port_specific_symbol_files),)
if grep '^# Appended to version file.' \
$(port_specific_symbol_files) /dev/null > /dev/null 2>&1; then \
cat $(port_specific_symbol_files) >> $@.tmp; \
else \
sed -n '1,/DO NOT DELETE/p' $@.tmp > tmp.top; \
sed -n '/DO NOT DELETE/,$$p' $@.tmp > tmp.bottom; \
cat tmp.top $(port_specific_symbol_files) tmp.bottom > $@.tmp; \
rm tmp.top tmp.bottom; \
fi;
endif
? Though, I think the initial and trailing whitespace is removed during
expansion (or already parsing of the vars), so even the
test "x$(port_specific_symbol_files)" != x
check should work right.