The header file has been included in link. C. Why can't I use LD to identify Mian and printf?

Linker LD

// Link. c

# Include <stdio. h>

# Include <stdlib. h>

Int main ()

{

Printf ("% F \ n", square (0.3 ));

System ("pause ");

Return 0;

}

// Square. c

Double square (Double X)

{

Return x * X;

}

Directly use LD to link the target file, and the output is as follows:

D: \ c traps and defects \ test> LD link. O square. O-o rlink.exe
Link. O: link. c :(. Text + 0xa): Undefined reference to '_ main'
Link. O: link. c :(. Text + 0x30): Undefined reference to 'printf'

Use GCC to link the target file. The output is as follows:

D: \ c traps and defects \ test> GCC link. O square. O-o rlink.exe

• The header file has been included in link. C. Why can't I use LD to identify Mian and printf?

By default, LD does not link any database.

When using the GCC link, GCC can automatically add some default links.

Use the -- verbose (-v) option of GCC to view the details of the compilation link.

We can see some of the default links of GCC, such

D: \ c traps and defects \ test> GCC link. O square. O-v-o rlink.exe
Using built-in specs.
Collect_gcc = gcc
Collect_lto_wrapper = F:/programes/mingw/bin/../libexec/GCC/mingw32/4.6.2/Lto-wrap
Per.exe
Target: mingw32
Configured with: ../gcc-4.6.2/configure -- enable-languages ages = C, C ++, Ada, Fortran, OBJ
C, obj-C ++ -- disable-sjlj-exceptions -- with-dwarf2 -- enable-shared -- enable-libgo
MP -- disable-win32-registry -- enable-libstdcxx-Debug -- enable-version-specific-R
Untime-Libs -- Build = mingw32 -- prefix =/mingw
Thread model: Win32
GCC version 4.6.2 (GCC)
Compiler_path = F:/programes/mingw/bin/../libexec/GCC/mingw32/4.6.2/; F:/programes/
Mingw/bin/../libexec/GCC/; F:/programes/mingw/bin/../lib/GCC/mingw32/4.6.2 /../../
../Mingw32/bin/
LIBRARY_PATH = F:/programes/mingw/bin/../lib/GCC/mingw32/4.6.2/; F:/programes/mingw
/Bin /.. /lib/GCC/; F:/programes/mingw/bin /.. /lib/GCC/mingw32/4.6.2 /.. /.. /.. /.. /min
Gw32/lib/; F:/programes/mingw/bin/../lib/GCC/mingw32/4.6.2 /../../../
Collect_gcc_options = '-v''-O' 'rlink.exe'-mtune = i386 ''-March = i386'
F:/programes/mingw/bin/../libexec/GCC/mingw32/4.6.2/collect2.exe-bdynamic-o r
Link.exe F:/programes/mingw/bin/../lib/GCC/mingw32/4.6.2/.../crt2.o F:/prog
Rames/mingw/bin/../lib/GCC/mingw32/4.6.2/crtbegin. O-lf:/programes/mingw/bin /../
LIB/GCC/mingw32/4.6.2-lf:/programes/mingw/bin/../lib/GCC-lf:/programes/mingw/B
In /.. /lib/GCC/mingw32/4.6.2 /.. /.. /.. /.. /mingw32/lib-lf:/programes/mingw/bin /../
LIB/GCC/mingw32/4.6.2/.../. Link. O square. O-lmingw32-lgcc_eh-lgcc-lmoldna
Me-lmingwex-lmsvcrt-ladvapi32-lshell32-luser32-lkernel32-lmingw32-lgcc_e
H-lgcc-lmoldname-lmingwex-lmsvcrt F:/programes/mingw/bin/../lib/GCC/mingw32/
4.6.2/crtend. o