[tor-bugs] #31769 [Core Tor/Tor]: -Wextra-semi causes build failure on debian bullseye

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#31769: -Wextra-semi causes build failure on debian bullseye
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 Reporter:  nickm                                |          Owner:  nickm
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.4.2.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  029-backport 035-backport            |  Actual Points:  .1
  040-backport 041-backport 042-should?          |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by nickm):

 This may be a debian-only issue: I have just noticed that apparently my
 fedora desktop also claims to have GCC 9.2.1, but compilation is passing.
 Apparently this happens because -Wextra-semi is detected as unsupported in
 the autoconf script:
 {{{
 configure:18768: checking whether the compiler accepts -Wextra-semi
 configure:18787: gcc -c -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
 -fstack-protector-all -Wstack-protector --param ssp-buffer-size=1 -fPIE
 -fasynchronous-unwind-tables -Wall -fno-strict-aliasing -Waddress -Warray-
 bounds -Wdate-time -Wdouble-promotion -Wduplicate-decl-specifier
 -Wduplicated-cond -Wextra -pedantic -Werror -Wextra-semi  conftest.c >&5
 cc1: error: command line option '-Wextra-semi' is valid for C++/ObjC++ but
 not for C [-Werror]
 cc1: all warnings being treated as errors
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31769#comment:5>
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