[patch] Remove superfluous /dev/null on grep line
Jonathan Wakely
jwakely@redhat.com
Wed Apr 6 08:50:00 GMT 2016
On 06/04/16 09:39 +0200, Eric Botcazou wrote:
>Hi,
>
>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.
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