无意中发现的：

C:\Users\my>gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=C:/Qt/Qt5.6.2/Tools/mingw492_32/bin/../libexec/gcc/i686-w64-mingw32/4.9.2/lto-wrapper.exe
Target: i686-w64-mingw32
Configured with: ../../../src/gcc-4.9.2/configure

--host=i686-w64-mingw32
--build=i686-w64-mingw32
--target=i686-w64-mingw32
--prefix=/mingw32
--with-sysroot=/c/mingw492/i686-492-posix-dwarf-rt_v3-rev1/mingw32
--with-gxx-include-dir=/mingw32/i686-w64-mingw32/include/c++
--enable-shared
--enable-static
--disable-multilib
--enable-languages=ada,c,c++,fortran,objc,obj-c++,lto
--enable-libstdcxx-time=yes
--enable-threads=posix
--enable-libgomp
--enable-libatomic
--enable-lto
--enable-graphite
--enable-checking=release
--enable-fully-dynamic-string
--enable-version-specific-runtime-libs
--disable-sjlj-exceptions
--with-dwarf2
--disable-isl-version-check
--disable-cloog-version-check
--disable-libstdcxx-pch
--disable-libstdcxx-debug
--enable-bootstrap
--disable-rpath
--disable-win32-registry
--disable-nls
--disable-werror
--disable-symvers
--with-gnu-as
--with-gnu-ld
--with-arch=i686
--with-tune=generic
--with-libiconv
--with-system-zlib
--with-gmp=/c/mingw492/prerequisites/i686-w64-mingw32-static
--with-mpfr=/c/mingw492/prerequisites/i686-w64-mingw32-static
--with-mpc=/c/mingw492/prerequisites/i686-w64-mingw32-static
--with-isl=/c/mingw492/prerequisites/i686-w64-mingw32-static
--with-cloog=/c/mingw492/prerequisites/i686-w64-mingw32-static
--enable-cloog-backend=isl
--with-pkgversion=‘i686-posix-dwarf-rev1, Built by MinGW-W64 project‘
--with-bugurl=http://sourceforge.net/projects/mingw-w64 CFLAGS=‘-O2

-pipe
-I/c/mingw492/i686-492-posix-dwarf-rt_v3-rev1/mingw32/opt/include
-I/c/mingw492/prerequisites/i686-zlib-static/include
-I/c/mingw492/prerequisites/i686-w64-mingw32-static/include‘ CXXFLAGS=‘-O2 -pipe
-I/c/mingw492/i686-492-posix-dwarf-rt_v3-rev1/mingw32/opt/include
-I/c/mingw492/prerequisites/i686-zlib-static/include
-I/c/mingw492/prerequisites/i686-w64-mingw32-static/include‘ CPPFLAGS= LDFLAGS=‘-pipe

-L/c/mingw492/i686-492-posix-dwarf-rt_v3-rev1/mingw32/opt/lib
-L/c/mingw492/prerequisites/i686-zlib-static/lib
-L/c/mingw492/prerequisites/i686-w64-mingw32-static/lib -Wl,--large-address-aware‘

Thread model: posix
gcc version 4.9.2 (i686-posix-dwarf-rev1, Built by MinGW-W64 project)

gcc默认使用的是dwarf格式