c - How can I assemble a minimal working MIPS program? -


i can run assembly code in simulator linker warning 

linking... ld: warning: cannot find entry symbol start; defaulting 80020000 post build...  done

why error solely assembly code , not c code same? how can change assembly make linker happy? i'd know statements not necessary can have minimal program?

i comment out these statement (that i'm not sure do):

#.frame $fp,40,$31      # vars= 16, regs= 2/0, args= 16, extra= 0 #.mask  0xc0000000,-4 #.fmask 0x00000000,0

my code (that translated c) is

    .file   1 "minimips.c"   # -g value = 8, cpu = 3000, isa = 1  # gnu c version cygnus-2.7.2-970404 (mips-mips-ecoff) compiled gnu c version cygnus-2.7.2-970404.  # options passed:  -msoft-float  # options enabled:  -fpeephole -ffunction-cse -fkeep-static-consts  # -fpcc-struct-return -fcommon -fverbose-asm -fgnu-linker -msoft-float  # -meb -mcpu=3000  gcc2_compiled.: __gnu_compiled_c:     .rdata     .align  2 $lc0:     .ascii  "result %d\000"     .text     .align  2     .globl  main     .ent    main main:     #.frame $fp,40,$31      # vars= 16, regs= 2/0, args= 16, extra= 0     #.mask  0xc0000000,-4     #.fmask 0x00000000,0     subu    $sp,$sp,40     sw  $31,36($sp)     sw  $fp,32($sp)     move    $fp,$sp     jal __main     li  $2,40                sw  $2,16($fp)     li  $2,40                sw  $2,20($fp)     lw  $2,16($fp)     lw  $3,20($fp)     addu    $2,$2,$3     sw  $2,24($fp)     la  $4,$lc0     lw  $5,24($fp)     jal printf     move    $2,$0     j   $l1 $l1:     move    $sp,$fp         # sp not trusted here     lw  $31,36($sp)     lw  $fp,32($sp)     addu    $sp,$sp,40     j   $31     .end    main

to begin i'm adding numbers. c code a+b=c.

update

when translated simpler program (without includes) can create project type assembly (and not combined c/asm).

it compiles , runs without linker error (but doesn't use printf)

gcc2_compiled.: __gnu_compiled_c:     .text     .align  2     .globl  main     .ent    main main:     .frame  $fp,40,$31      # vars= 16, regs= 2/0, args= 16, extra= 0     .mask   0xc0000000,-4     .fmask  0x00000000,0     subu    $sp,$sp,40     sw  $31,36($sp)     sw  $fp,32($sp)     move    $fp,$sp     jal __main     li  $2,15           # 0x0000000a     sw  $2,16($fp)     li  $2,20           # 0x00000014     sw  $2,20($fp)     lw  $2,16($fp)     lw  $3,20($fp)     addu    $2,$2,$3     sw  $2,24($fp)     move    $2,$0     j   $l1 $l1:     move    $sp,$fp         # sp not trusted here     lw  $31,36($sp)     lw  $fp,32($sp)     addu    $sp,$sp,40     j   $31     .end    main

the c library defines special symbol called start program starts execution. linker expects find symbol, use program entry point.

you didn't define start linker complains , gives default value. default first instruction of code, that's why program still works.


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