在GCC 10.2.1而不是GCC 8.3.0上首次定义的&的多重定义 [英] "Multiple definition of" "first defined here" on GCC 10.2.1 but not GCC 8.3.0

查看:25
本文介绍了在GCC 10.2.1而不是GCC 8.3.0上首次定义的&的多重定义的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我查看了Stackoverflow和更广泛的Internet,发现此错误的最常见原因是声明(int var = 1;)和定义(int var;)合并,并包括.h文件中的.c文件。

我刚刚从一个文件拆分成几个文件的小项目没有做任何这些事情。我非常困惑。

我复制了项目并删除了副本中的所有代码(这很有趣),直到我到达此处:

main.c

#include "a.h"

int main() {
    
}

A.H

#ifndef A_H
#define A_H

int test;

#endif

交流

#include "a.h"

就像它得到的那样规范,对吗?然而...

$ rm *.o; gcc -g -c a.c; gcc -g -c main.c; gcc -o main main.o a.o
/usr/bin/ld: a.o:/.../a.h:5: multiple definition of `test'; main.o:/.../a.h:5: first defined here
collect2: error: ld returned 1 exit status

Wat:(

就在这个时候,我开始质疑我的配置,并尝试了另一台计算机,通过NFS访问完全相同的文件。

$ rm *.o; gcc -g -c a.c; gcc -g -c main.c; gcc -o main main.o a.o
$ ./main
$ echo $?
0

哦,不。我在第一台机器上打碎了什么东西...

希望我的问题是在GCC 8.3.0(正在工作)GCC 10.2.1(失败)之间发生了悄悄的变化?也许新版本的GCC默认使用更新的C标准或其他什么,这规定了这一领域的不同行为?

或者,它可能与配置相关(这都是常见的Debian)。以下是两个版本的gcc -dumpspecs的输出:

8.3.0:

数据-lang="js"数据-隐藏="真"数据-控制台="假"数据-巴贝尔="假">
$ gcc --version
gcc (Debian 8.3.0-6) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gcc -dumpspecs
*asm:
%{m16|m32:--32}  %{m16|m32|mx32:;:--64}  %{mx32:--x32}  %{msse2avx:%{!mavx:-msse2avx}}

*asm_debug:
%{%:debug-level-gt(0):%{gstabs*:--gstabs}%{!gstabs*:%{g*:--gdwarf2}}} %{fdebug-prefix-map=*:--debug-prefix-map %*}

*asm_final:
%{gsplit-dwarf: 
   objcopy --extract-dwo     %{c:%{o*:%*}%{!o*:%b%O}}%{!c:%U%O}      %{c:%{o*:%:replace-extension(%{o*:%*} .dwo)}%{!o*:%b.dwo}}%{!c:%b.dwo} 
   objcopy --strip-dwo       %{c:%{o*:%*}%{!o*:%b%O}}%{!c:%U%O}     }

*asm_options:
%{-target-help:%:print-asm-header()} %{v} %{w:-W} %{I*}  %{gz|gz=zlib:--compress-debug-sections=zlib} %{gz=none:--compress-debug-sections=none} %{gz=zlib-gnu:--compress-debug-sections=zlib-gnu} %a %Y %{c:%W{o*}%{!o*:-o %w%b%O}}%{!c:-o %d%w%u%O}

*invoke_as:
%{!fwpa*:   %{fcompare-debug=*|fdump-final-insns=*:%:compare-debug-dump-opt()}   %{!S:-o %|.s |
 as %(asm_options) %m.s %A }  }

*cpp:
%{posix:-D_POSIX_SOURCE} %{pthread:-D_REENTRANT}

*cpp_options:
%(cpp_unique_options) %1 %{m*} %{std*&ansi&trigraphs} %{W*&pedantic*} %{w} %{f*} %{g*:%{%:debug-level-gt(0):%{g*} %{!fno-working-directory:-fworking-directory}}} %{O*} %{undef} %{save-temps*:-fpch-preprocess}

*cpp_debug_options:
%{d*}

*cpp_unique_options:
%{!Q:-quiet} %{nostdinc*} %{C} %{CC} %{v} %{I*&F*} %{P} %I %{MD:-MD %{!o:%b.d}%{o*:%.d%*}} %{MMD:-MMD %{!o:%b.d}%{o*:%.d%*}} %{M} %{MM} %{MF*} %{MG} %{MP} %{MQ*} %{MT*} %{!E:%{!M:%{!MM:%{!MT:%{!MQ:%{MD|MMD:%{o*:-MQ %*}}}}}}} %{remap} %{g3|ggdb3|gstabs3|gxcoff3|gvms3:-dD} %{!iplugindir*:%{fplugin*:%:find-plugindir()}} %{H} %C %{D*&U*&A*} %{i*} %Z %i %{E|M|MM:%W{o*}}

*trad_capable_cpp:
cc1 -E %{traditional|traditional-cpp:-traditional-cpp}

*cc1:
%{!mandroid|tno-android-cc:%(cc1_cpu) %{profile:-p};:%(cc1_cpu) %{profile:-p} %{!mglibc:%{!muclibc:%{!mbionic: -mbionic}}} %{!fno-pic:%{!fno-PIC:%{!fpic:%{!fPIC: -fPIC}}}}}

*cc1_options:
%{pg:%{fomit-frame-pointer:%e-pg and -fomit-frame-pointer are incompatible}} %{!iplugindir*:%{fplugin*:%:find-plugindir()}} %1 %{!Q:-quiet} %{!dumpbase:-dumpbase %B} %{d*} %{m*} %{aux-info*} %{fcompare-debug-second:%:compare-debug-auxbase-opt(%b)}  %{!fcompare-debug-second:%{c|S:%{o*:-auxbase-strip %*}%{!o*:-auxbase %b}}}%{!c:%{!S:-auxbase %b}}  %{g*} %{O*} %{W*&pedantic*} %{w} %{std*&ansi&trigraphs} %{v:-version} %{pg:-p} %{p} %{f*} %{undef} %{Qn:-fno-ident} %{Qy:} %{-help:--help} %{-target-help:--target-help} %{-version:--version} %{-help=*:--help=%*} %{!fsyntax-only:%{S:%W{o*}%{!o*:-o %b.s}}} %{fsyntax-only:-o %j} %{-param*} %{coverage:-fprofile-arcs -ftest-coverage} %{fprofile-arcs|fprofile-generate*|coverage:   %{!fprofile-update=single:     %{pthread:-fprofile-update=prefer-atomic}}}

*cc1plus:


*link_gcc_c_sequence:
%{static|static-pie:--start-group} %G %L    %{static|static-pie:--end-group}%{!static:%{!static-pie:%G}}

*link_ssp:
%{fstack-protector|fstack-protector-all|fstack-protector-strong|fstack-protector-explicit:}

*endfile:
%{!mandroid|tno-android-ld:%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s}    %{mpc32:crtprec32.o%s}    %{mpc64:crtprec64.o%s}    %{mpc80:crtprec80.o%s} %{fvtable-verify=none:%s;      fvtable-verify=preinit:vtv_end_preinit.o%s;      fvtable-verify=std:vtv_end.o%s}    %{static:crtend.o%s;      shared|static-pie|!no-pie:crtendS.o%s;      :crtend.o%s}    crtn.o%s    %{fopenacc|fopenmp:crtoffloadend%O%s};:%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s}    %{mpc32:crtprec32.o%s}    %{mpc64:crtprec64.o%s}    %{mpc80:crtprec80.o%s} %{shared: crtend_so%O%s;: crtend_android%O%s}}

*link:
%{!r:--build-id} %{!static|static-pie:--eh-frame-hdr} %{!mandroid|tno-android-ld:%{m16|m32|mx32:;:-m elf_x86_64}                    %{m16|m32:-m elf_i386}                    %{mx32:-m elf32_x86_64}   --hash-style=gnu   %{shared:-shared}   %{!shared:     %{!static:       %{!static-pie:     %{rdynamic:-export-dynamic}     %{m16|m32:-dynamic-linker %{muclibc:/lib/ld-uClibc.so.0;:%{mbionic:/system/bin/linker;:%{mmusl:/lib/ld-musl-i386.so.1;:/lib/ld-linux.so.2}}}}   %{m16|m32|mx32:;:-dynamic-linker %{muclibc:/lib/ld64-uClibc.so.0;:%{mbionic:/system/bin/linker64;:%{mmusl:/lib/ld-musl-x86_64.so.1;:/lib64/ld-linux-x86-64.so.2}}}}       %{mx32:-dynamic-linker %{muclibc:/lib/ldx32-uClibc.so.0;:%{mbionic:/system/bin/linkerx32;:%{mmusl:/lib/ld-musl-x32.so.1;:/libx32/ld-linux-x32.so.2}}}}}}     %{static:-static} %{static-pie:-static -pie --no-dynamic-linker -z text}};:%{m16|m32|mx32:;:-m elf_x86_64}                    %{m16|m32:-m elf_i386}                    %{mx32:-m elf32_x86_64}   --hash-style=gnu   %{shared:-shared}   %{!shared:     %{!static:       %{!static-pie:        %{rdynamic:-export-dynamic}     %{m16|m32:-dynamic-linker %{muclibc:/lib/ld-uClibc.so.0;:%{mbionic:/system/bin/linker;:%{mmusl:/lib/ld-musl-i386.so.1;:/lib/ld-linux.so.2}}}}   %{m16|m32|mx32:;:-dynamic-linker %{muclibc:/lib/ld64-uClibc.so.0;:%{mbionic:/system/bin/linker64;:%{mmusl:/lib/ld-musl-x86_64.so.1;:/lib64/ld-linux-x86-64.so.2}}}}       %{mx32:-dynamic-linker %{muclibc:/lib/ldx32-uClibc.so.0;:%{mbionic:/system/bin/linkerx32;:%{mmusl:/lib/ld-musl-x32.so.1;:/libx32/ld-linux-x32.so.2}}}}}}     %{static:-static} %{static-pie:-static -pie --no-dynamic-linker -z text}} %{shared: -Bsymbolic}}

*lib:
%{!mandroid|tno-android-ld:%{pthread:-lpthread} %{shared:-lc}    %{!shared:%{profile:-lc_p}%{!profile:-lc}};:%{shared:-lc}    %{!shared:%{profile:-lc_p}%{!profile:-lc}} %{!static: -ldl}}

*link_gomp:


*libgcc:
%{static|static-libgcc|static-pie:-lgcc -lgcc_eh}%{!static:%{!static-libgcc:%{!static-pie:%{!shared-libgcc:-lgcc --push-state --as-needed -lgcc_s --pop-state}%{shared-libgcc:-lgcc_s%{!shared: -lgcc}}}}}

*startfile:
%{!mandroid|tno-android-ld:%{shared:;      pg|p|profile:%{static-pie:grcrt1.o%s;:gcrt1.o%s};      static:crt1.o%s;      static-pie:rcrt1.o%s;      !no-pie:Scrt1.o%s;      :crt1.o%s}    crti.o%s    %{static:crtbeginT.o%s;      shared|static-pie|!no-pie:crtbeginS.o%s;      :crtbegin.o%s}    %{fvtable-verify=none:%s;      fvtable-verify=preinit:vtv_start_preinit.o%s;      fvtable-verify=std:vtv_start.o%s}    %{fopenacc|fopenmp:crtoffloadbegin%O%s};:%{shared: crtbegin_so%O%s;:  %{static: crtbegin_static%O%s;: crtbegin_dynamic%O%s}}}

*cross_compile:
0

*version:
8.3.0

*multilib:
. !m32 !m64 !mx32;32:../lib32:i386-linux-gnu m32 !m64 !mx32;64:../lib:x86_64-linux-gnu !m32 m64 !mx32;x32:../libx32:x86_64-linux-gnux32 !m32 !m64 mx32;

*multilib_defaults:
m64

*multilib_extra:


*multilib_matches:
m32 m32;m64 m64;mx32 mx32;

*multilib_exclusions:


*multilib_options:
m32/m64/mx32

*multilib_reuse:


*linker:
collect2

*linker_plugin_file:


*lto_wrapper:


*lto_gcc:


*post_link:


*link_libgcc:
%D

*md_exec_prefix:


*md_startfile_prefix:


*md_startfile_prefix_1:


*startfile_prefix_spec:


*sysroot_spec:
--sysroot=%R

*sysroot_suffix_spec:


*sysroot_hdrs_suffix_spec:


*self_spec:


*cc1_cpu:
%{march=native:%>march=native %:local_cpu_detect(arch)   %{!mtune=*:%>mtune=native %:local_cpu_detect(tune)}} %{mtune=native:%>mtune=native %:local_cpu_detect(tune)}

*link_command:
%{!fsyntax-only:%{!c:%{!M:%{!MM:%{!E:%{!S:    %(linker) %{!fno-use-linker-plugin:%{!fno-lto:     -plugin %(linker_plugin_file)     -plugin-opt=%(lto_wrapper)     -plugin-opt=-fresolution=%u.res     %{!nostdlib:%{!nodefaultlibs:%:pass-through-libs(%(link_gcc_c_sequence))}}     }}%{flto|flto=*:%<fcompare-debug*}     %{flto} %{fno-lto} %{flto=*} %l %{static|shared|r:;!no-pie:-pie} %{fuse-ld=*:-fuse-ld=%*}  %{gz|gz=zlib:--compress-debug-sections=zlib} %{gz=none:--compress-debug-sections=none} %{gz=zlib-gnu:--compress-debug-sections=zlib-gnu} %X %{o*} %{e*} %{N} %{n} %{r}    %{s} %{t} %{u*} %{z} %{Z} %{!nostdlib:%{!nostartfiles:%S}}     %{static|no-pie|static-pie:} %{L*} %(mfwrap) %(link_libgcc) %{fvtable-verify=none:} %{fvtable-verify=std:   %e-fvtable-verify=std is not supported in this configuration} %{fvtable-verify=preinit:   %e-fvtable-verify=preinit is not supported in this configuration} %{!nostdlib:%{!nodefaultlibs:%{%:sanitize(address):%{!shared:libasan_preinit%O%s} %{static-libasan:%{!shared:-Bstatic --whole-archive -lasan --no-whole-archive -Bdynamic}}%{!static-libasan:-lasan}}     %{%:sanitize(thread):%{!shared:libtsan_preinit%O%s} %{static-libtsan:%{!shared:-Bstatic --whole-archive -ltsan --no-whole-archive -Bdynamic}}%{!static-libtsan:-ltsan}}     %{%:sanitize(leak):%{!shared:liblsan_preinit%O%s} %{static-liblsan:%{!shared:-Bstatic --whole-archive -llsan --no-whole-archive -Bdynamic}}%{!static-liblsan:-llsan}}}} %o %{!nostdlib:%{!nodefaultlibs:%{mmpx:%{fcheck-pointer-bounds:    %{static:--whole-archive -lmpx --no-whole-archive %:include(libmpx.spec)%(link_libmpx)}    %{!static:%{static-libmpx:-Bstatic --whole-archive}    %{!static-libmpx:--push-state --no-as-needed} -lmpx     %{!static-libmpx:--pop-state}     %{static-libmpx:--no-whole-archive -Bdynamic %:include(libmpx.spec)%(link_libmpx)}}}}%{mmpx:%{fcheck-pointer-bounds:%{!fno-chkp-use-wrappers:    %{static:-lmpxwrappers}    %{!static:%{static-libmpxwrappers:-Bstatic}    -lmpxwrappers %{static-libmpxwrappers: -Bdynamic}}}}}}} %{mmpx:%{fcheck-pointer-bounds:%{!static:%{m16|m32|mx32:;:-z bndplt }}}}     %{fopenacc|fopenmp|%:gt(%{ftree-parallelize-loops=*:%*} 1):        %:include(libgomp.spec)%(link_gomp)}    %{fgnu-tm:%:include(libitm.spec)%(link_itm)}    %(mflib)  %{fsplit-stack: --wrap=pthread_create}    %{fprofile-arcs|fprofile-generate*|coverage:-lgcov} %{!nostdlib:%{!nodefaultlibs:%{%:sanitize(address): %{static-libasan|static:%:include(libsanitizer.spec)%(link_libasan)}    %{static:%ecannot specify -static with -fsanitize=address}}    %{%:sanitize(thread): %{static-libtsan|static:%:include(libsanitizer.spec)%(link_libtsan)}    %{static:%ecannot specify -static with -fsanitize=thread}}    %{%:sanitize(undefined):%{static-libubsan:-Bstatic} -lubsan %{static-libubsan:-Bdynamic} %{static-libubsan|static:%:include(libsanitizer.spec)%(link_libubsan)}}    %{%:sanitize(leak): %{static-liblsan|static:%:include(libsanitizer.spec)%(link_liblsan)}}}}     %{!nostdlib:%{!nodefaultlibs:%(link_ssp) %(link_gcc_c_sequence)}}    %{!nostdlib:%{!nostartfiles:%E}} %{T*}  
%(post_link) }}}}}}

10.2.1:

数据-lang="js"数据-隐藏="真"数据-控制台="假"数据-巴贝尔="假">
$ gcc --version
gcc (Debian 10.2.1-6) 10.2.1 20210110
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gcc -dumpspecs
*asm:
%{m16|m32:--32}  %{m16|m32|mx32:;:--64}  %{mx32:--x32}  %{msse2avx:%{!mavx:-msse2avx}}

*asm_debug:
%{%:debug-level-gt(0):%{gstabs*:--gstabs}%{!gstabs*:%{g*:--gdwarf2}}} %{fdebug-prefix-map=*:--debug-prefix-map %*}

*asm_final:
%{gsplit-dwarf: 
   objcopy --extract-dwo     %{c:%{o*:%*}%{!o*:%b%O}}%{!c:%U%O}      %{c:%{o*:%:replace-extension(%{o*:%*} .dwo)}%{!o*:%b.dwo}}%{!c:%b.dwo} 
   objcopy --strip-dwo       %{c:%{o*:%*}%{!o*:%b%O}}%{!c:%U%O}     }

*asm_options:
%{-target-help:%:print-asm-header()} %{v} %{w:-W} %{I*}  %{gz|gz=zlib:--compress-debug-sections=zlib} %{gz=none:--compress-debug-sections=none} %{gz=zlib-gnu:--compress-debug-sections=zlib-gnu} %a %Y %{c:%W{o*}%{!o*:-o %w%b%O}}%{!c:-o %d%w%u%O}

*invoke_as:
%{!fwpa*:   %{fcompare-debug=*|fdump-final-insns=*:%:compare-debug-dump-opt()}   %{!S:-o %|.s |
 as %(asm_options) %m.s %A }  }

*cpp:
%{posix:-D_POSIX_SOURCE} %{pthread:-D_REENTRANT}

*cpp_options:
%(cpp_unique_options) %1 %{m*} %{std*&ansi&trigraphs} %{W*&pedantic*} %{w} %{f*} %{g*:%{%:debug-level-gt(0):%{g*} %{!fno-working-directory:-fworking-directory}}} %{O*} %{undef} %{save-temps*:-fpch-preprocess} %(distro_defaults)

*cpp_debug_options:
%{d*}

*cpp_unique_options:
%{!Q:-quiet} %{nostdinc*} %{C} %{CC} %{v} %@{I*&F*} %{P} %I %{MD:-MD %{!o:%b.d}%{o*:%.d%*}} %{MMD:-MMD %{!o:%b.d}%{o*:%.d%*}} %{M} %{MM} %{MF*} %{MG} %{MP} %{MQ*} %{MT*} %{!E:%{!M:%{!MM:%{!MT:%{!MQ:%{MD|MMD:%{o*:-MQ %*}}}}}}} %{remap} %{g3|ggdb3|gstabs3|gxcoff3|gvms3:-dD} %{!iplugindir*:%{fplugin*:%:find-plugindir()}} %{H} %C %{D*&U*&A*} %{i*} %Z %i %{E|M|MM:%W{o*}}

*trad_capable_cpp:
cc1 -E %{traditional|traditional-cpp:-traditional-cpp}

*cc1:
%{!mandroid|tno-android-cc:%(cc1_cpu) %{profile:-p};:%(cc1_cpu) %{profile:-p} %{!mglibc:%{!muclibc:%{!mbionic: -mbionic}}} %{!fno-pic:%{!fno-PIC:%{!fpic:%{!fPIC: -fPIC}}}}}

*cc1_options:
%{pg:%{fomit-frame-pointer:%e-pg and -fomit-frame-pointer are incompatible}} %{!iplugindir*:%{fplugin*:%:find-plugindir()}} %1 %{!Q:-quiet} %{!dumpbase:-dumpbase %B} %{d*} %{m*} %{aux-info*} %{fcompare-debug-second:%:compare-debug-auxbase-opt(%b)}  %{!fcompare-debug-second:%{c|S:%{o*:-auxbase-strip %*}%{!o*:-auxbase %b}}}%{!c:%{!S:-auxbase %b}}  %{g*} %{O*} %{W*&pedantic*} %{w} %{std*&ansi&trigraphs} %{v:-version} %{pg:-p} %{p} %{f*} %{undef} %{Qn:-fno-ident} %{Qy:} %{-help:--help} %{-target-help:--target-help} %{-version:--version} %{-help=*:--help=%*} %{!fsyntax-only:%{S:%W{o*}%{!o*:-o %b.s}}} %{fsyntax-only:-o %j} %{-param*} %{coverage:-fprofile-arcs -ftest-coverage} %{fprofile-arcs|fprofile-generate*|coverage:   %{!fprofile-update=single:     %{pthread:-fprofile-update=prefer-atomic}}}

*cc1plus:


*link_gcc_c_sequence:
%{static|static-pie:--start-group} %G %{!nolibc:%L}    %{static|static-pie:--end-group}%{!static:%{!static-pie:%G}}

*distro_defaults:
%{!fno-asynchronous-unwind-tables:-fasynchronous-unwind-tables}

*link_ssp:
%{fstack-protector|fstack-protector-all|fstack-protector-strong|fstack-protector-explicit:}

*endfile:
%{!mandroid|tno-android-ld:%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s}    %{mpc32:crtprec32.o%s}    %{mpc64:crtprec64.o%s}    %{mpc80:crtprec80.o%s} %{!static:%{fvtable-verify=none:%s;      fvtable-verify=preinit:vtv_end_preinit.o%s;      fvtable-verify=std:vtv_end.o%s}}    %{static:crtend.o%s;      shared|static-pie|!no-pie:crtendS.o%s;      :crtend.o%s} crtn.o%s %{fopenacc|fopenmp:crtoffloadend%O%s};:%{Ofast|ffast-math|funsafe-math-optimizations:crtfastmath.o%s}    %{mpc32:crtprec32.o%s}    %{mpc64:crtprec64.o%s}    %{mpc80:crtprec80.o%s} %{shared: crtend_so%O%s;: crtend_android%O%s}}

*link:
%{!r:--build-id} %{!static|static-pie:--eh-frame-hdr} %{!mandroid|tno-android-ld:%{m16|m32|mx32:;:-m elf_x86_64}                    %{m16|m32:-m elf_i386}                    %{mx32:-m elf32_x86_64}   --hash-style=gnu   --as-needed   %{shared:-shared}   %{!shared:     %{!static:       %{!static-pie:       %{rdynamic:-export-dynamic}     %{m16|m32:-dynamic-linker %{muclibc:/lib/ld-uClibc.so.0;:%{mbionic:/system/bin/linker;:%{mmusl:/lib/ld-musl-i386.so.1;:/lib/ld-linux.so.2}}}}     %{m16|m32|mx32:;:-dynamic-linker %{muclibc:/lib/ld64-uClibc.so.0;:%{mbionic:/system/bin/linker64;:%{mmusl:/lib/ld-musl-x86_64.so.1;:/lib64/ld-linux-x86-64.so.2}}}}     %{mx32:-dynamic-linker %{muclibc:/lib/ldx32-uClibc.so.0;:%{mbionic:/system/bin/linkerx32;:%{mmusl:/lib/ld-musl-x32.so.1;:/libx32/ld-linux-x32.so.2}}}}}}     %{static:-static} %{static-pie:-static -pie --no-dynamic-linker -z text}};:%{m16|m32|mx32:;:-m elf_x86_64}                    %{m16|m32:-m elf_i386}                    %{mx32:-m elf32_x86_64}   --hash-style=gnu   --as-needed   %{shared:-shared}   %{!shared:     %{!static:       %{!static-pie:  %{rdynamic:-export-dynamic}     %{m16|m32:-dynamic-linker %{muclibc:/lib/ld-uClibc.so.0;:%{mbionic:/system/bin/linker;:%{mmusl:/lib/ld-musl-i386.so.1;:/lib/ld-linux.so.2}}}}     %{m16|m32|mx32:;:-dynamic-linker %{muclibc:/lib/ld64-uClibc.so.0;:%{mbionic:/system/bin/linker64;:%{mmusl:/lib/ld-musl-x86_64.so.1;:/lib64/ld-linux-x86-64.so.2}}}}       %{mx32:-dynamic-linker %{muclibc:/lib/ldx32-uClibc.so.0;:%{mbionic:/system/bin/linkerx32;:%{mmusl:/lib/ld-musl-x32.so.1;:/libx32/ld-linux-x32.so.2}}}}}}     %{static:-static} %{static-pie:-static -pie --no-dynamic-linker -z text}} %{shared: -Bsymbolic}}

*lib:
%{!mandroid|tno-android-ld:%{pthread:-lpthread} %{shared:-lc}    %{!shared:%{profile:-lc_p}%{!profile:-lc}};:%{shared:-lc}    %{!shared:%{profile:-lc_p}%{!profile:-lc}} %{!static: -ldl}}

*link_gomp:


*libgcc:
%{static|static-libgcc|static-pie:-lgcc -lgcc_eh}%{!static:%{!static-libgcc:%{!static-pie:%{!shared-libgcc:-lgcc --push-state --as-needed -lgcc_s --pop-state}%{shared-libgcc:-lgcc_s%{!shared: -lgcc}}}}}

*startfile:
%{!mandroid|tno-android-ld:%{shared:;      pg|p|profile:%{static-pie:grcrt1.o%s;:gcrt1.o%s};      static:crt1.o%s;      static-pie:rcrt1.o%s;      !no-pie:Scrt1.o%s;      :crt1.o%s} crti.o%s    %{static:crtbeginT.o%s;      shared|static-pie|!no-pie:crtbeginS.o%s;      :crtbegin.o%s}    %{fvtable-verify=none:%s;      fvtable-verify=preinit:vtv_start_preinit.o%s;      fvtable-verify=std:vtv_start.o%s} %{fopenacc|fopenmp:crtoffloadbegin%O%s};:%{shared: crtbegin_so%O%s;:  %{static: crtbegin_static%O%s;: crtbegin_dynamic%O%s}}}

*cross_compile:
0

*version:
10.2.1

*multilib:
. !m32 !m64 !mx32;32:../lib32:i386-linux-gnu m32 !m64 !mx32;64:../lib:x86_64-linux-gnu !m32 m64 !mx32;x32:../libx32:x86_64-linux-gnux32 !m32 !m64 mx32;

*multilib_defaults:
m64

*multilib_extra:


*multilib_matches:
m32 m32;m64 m64;mx32 mx32;

*multilib_exclusions:


*multilib_options:
m32/m64/mx32

*multilib_reuse:


*linker:
collect2

*linker_plugin_file:


*lto_wrapper:


*lto_gcc:


*post_link:


*link_libgcc:
%D

*md_exec_prefix:


*md_startfile_prefix:


*md_startfile_prefix_1:


*startfile_prefix_spec:


*sysroot_spec:
--sysroot=%R

*sysroot_suffix_spec:


*sysroot_hdrs_suffix_spec:


*self_spec:


*cc1_cpu:
%{march=native:%>march=native %:local_cpu_detect(arch)   %{!mtune=*:%>mtune=native %:local_cpu_detect(tune)}} %{mtune=native:%>mtune=native %:local_cpu_detect(tune)}

*link_command:
%{!fsyntax-only:%{!c:%{!M:%{!MM:%{!E:%{!S:    %(linker) %{!fno-use-linker-plugin:%{!fno-lto:     -plugin %(linker_plugin_file)     -plugin-opt=%(lto_wrapper)     -plugin-opt=-fresolution=%u.res     %{flinker-output=*:-plugin-opt=-linker-output-known}     %{!nostdlib:%{!nodefaultlibs:%:pass-through-libs(%(link_gcc_c_sequence))}}     }}%{flto|flto=*:%<fcompare-debug*}     %{flto} %{fno-lto} %{flto=*} %l %{static|shared|r:;!no-pie:-pie} %{fuse-ld=*:-fuse-ld=%*}  %{gz|gz=zlib:--compress-debug-sections=zlib} %{gz=none:--compress-debug-sections=none} %{gz=zlib-gnu:--compress-debug-sections=zlib-gnu} %X %{o*} %{e*} %{N} %{n} %{r}    %{s} %{t} %{u*} %{z} %{Z} %{!nostdlib:%{!r:%{!nostartfiles:%S}}}     %{static|no-pie|static-pie:} %@{L*} %(mfwrap) %(link_libgcc) %{fvtable-verify=none:} %{fvtable-verify=std:   %e-fvtable-verify=std is not supported in this configuration} %{fvtable-verify=preinit:   %e-fvtable-verify=preinit is not supported in this configuration} %{!nostdlib:%{!r:%{!nodefaultlibs:%{%:sanitize(address):%{!shared:libasan_preinit%O%s} %{static-libasan:%{!shared:-Bstatic --whole-archive -lasan --no-whole-archive -Bdynamic}}%{!static-libasan:%{!fuse-ld=gold:--push-state} --no-as-needed -lasan %{fuse-ld=gold:--as-needed;:--pop-state}}}     %{%:sanitize(thread):%{!shared:libtsan_preinit%O%s} %{static-libtsan:%{!shared:-Bstatic --whole-archive -ltsan --no-whole-archive -Bdynamic}}%{!static-libtsan:%{!fuse-ld=gold:--push-state} --no-as-needed -ltsan %{fuse-ld=gold:--as-needed;:--pop-state}}}     %{%:sanitize(leak):%{!shared:liblsan_preinit%O%s} %{static-liblsan:%{!shared:-Bstatic --whole-archive -llsan --no-whole-archive -Bdynamic}}%{!static-liblsan:%{!fuse-ld=gold:--push-state} --no-as-needed -llsan %{fuse-ld=gold:--as-needed;:--pop-state}}}}}} %o      %{fopenacc|fopenmp|%:gt(%{ftree-parallelize-loops=*:%*} 1):     %:include(libgomp.spec)%(link_gomp)}    %{fgnu-tm:%:include(libitm.spec)%(link_itm)}    %(mflib)  %{fsplit-stack: --wrap=pthread_create}    %{fprofile-arcs|fprofile-generate*|coverage:-lgcov} %{!nostdlib:%{!r:%{!nodefaultlibs:%{%:sanitize(address): %{static-libasan|static:%:include(libsanitizer.spec)%(link_libasan)}    %{static:%ecannot specify -static with -fsanitize=address}}    %{%:sanitize(thread): %{static-libtsan|static:%:include(libsanitizer.spec)%(link_libtsan)}    %{static:%ecannot specify -static with -fsanitize=thread}}    %{%:sanitize(undefined):%{static-libubsan:-Bstatic} %{!static-libubsan:--push-state --no-as-needed} -lubsan  %{static-libubsan:-Bdynamic} %{!static-libubsan:--pop-state} %{static-libubsan|static:%:include(libsanitizer.spec)%(link_libubsan)}}    %{%:sanitize(leak): %{static-liblsan|static:%:include(libsanitizer.spec)%(link_liblsan)}}}}}     %{!nostdlib:%{!r:%{!nodefaultlibs:%(link_ssp) %(link_gcc_c_sequence)}}}    %{!nostdlib:%{!r:%{!nostartfiles:%E}}} %{T*}  
%(post_link) }}}}}}

推荐答案

是,行为发生了变化。

在C中,您应该只在一个翻译单元中定义一个全局变量,其他要访问该变量的翻译单元应将其声明为。

在您的代码中,a.h同时包含在a.c和main.c中,因此变量被定义了两次。要解决此问题,您应该将A.H中的";int test";更改为";extern int test";,然后将";int test";添加到A.C以精确定义变量一次。


在C中,不初始化变量的全局变量的定义被认为是暂定的。在同一个编译单元中可以有一个变量的多个暂定定义。标准C中不允许不同编译单元中的多个暂定定义,但Unix系统上的C编译器过去允许这样做。

GCC的旧版本默认允许在不同的编译单元中对全局变量进行多个张量定义(但不允许多个非试探性定义)。GCC-10没有。您可以使用命令行选项&fCommon";恢复旧的行为,但不建议这样做。

这篇关于在GCC 10.2.1而不是GCC 8.3.0上首次定义的&的多重定义的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

查看全文
相关文章
服务器开发最新文章
热门教程
热门工具
登录 关闭
扫码关注1秒登录
发送“验证码”获取 | 15天全站免登陆