https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64864
Bug ID: 64864 Summary: [5 Regression] preprocessor linemarkers break configure checks Product: gcc Version: 5.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: preprocessor Assignee: unassigned at gcc dot gnu.org Reporter: trippels at gcc dot gnu.org CC: dodji at gcc dot gnu.org For example (this happens for many projects that check for the boost version): ... checking for working strtod... yes checking for gettimeofday... yes checking for Boost headers version >= 1.36.0... yes checking for Boost's header version... configure: error: invalid value: boost_major_version= markus@x4 core % cat test.cpp #include <boost/version.hpp> boost-lib-version = BOOST_LIB_VERSION markus@x4 core % g++ -E test.cpp # 1 "test.cpp" # 1 "<built-in>" # 1 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 1 "<command-line>" 2 # 1 "test.cpp" # 1 "/usr/include/boost/version.hpp" 1 3 4 # 2 "test.cpp" 2 boost-lib-version = # 2 "test.cpp" 3 4 "1_56" markus@x4 core % /usr/x86_64-pc-linux-gnu/gcc-bin/4.9.2/g++ -E test.cpp # 1 "test.cpp" # 1 "<built-in>" # 1 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 1 "<command-line>" 2 # 1 "test.cpp" # 1 "/usr/include/boost/version.hpp" 1 3 4 # 2 "test.cpp" 2 boost-lib-version = "1_56" I know that these linemarkers are valid. But is it really necessary that they appear in the middle of statements? Using -P is a workaround, that apparently nobody uses in configure scripts. See also PR64604.