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Forum: ARM programming with GCC/GNU tools undefined reference to sprintf?


Author: Mike P (Guest)
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why can't it find sprintf?  can't believe this!

Mike@l2200 ~/Example
$ make test
..linking
arm-elf-ld -v -Map main.map -nostartfiles -T simple.cmd -L 
/gnude/arm-elf/lib -l
c -lg -L /gnude/lib/gcc-lib/arm-elf/3.3.1 -lgcc  -o main.out  start.o 
ivt.o libc
.a main.o Init22.o LCD.o RTC.o Serial.o Timer.o PWM.o Keypad.o Chars.o 
Delay.o
GNU ld version 2.14 20030612
main.o(.text+0x16c): In function `__main':
: undefined reference to `sprintf'
main.o(.text+0x198): In function `__main':
: undefined reference to `sprintf'
main.o(.text+0x1d8): In function `__main':
: undefined reference to `sprintf'
main.o(.text+0x1f8): In function `__main':
: undefined reference to `strcat'
main.o(.text+0x238): In function `__main':
: undefined reference to `sprintf'

C:\cygwin\gnude\arm-elf\lib
C:\cygwin\gnude\lib\gcc-lib\arm-elf\3.3.1


#include <stdlib.h>
#include <stdio.h>
#include <string.h>

static void ShowIt(void)
{
  char* s;
  char sOutBuffer[100];
  s = (char*) &sOutBuffer;

  sprintf(s, "%d:%.2d:%.2d", 1, 2, 3);
}

thank you for your help!

Author: Hans Mayer (Company: mayer) (oe1smc)
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dear mike

i haven't an answer, but why so complicated:

>>  s = (char*) &sOutBuffer;

much more easy.

s = sOutBuffer ;

kind regards
hans

--

Author: Rolf Magnus (Guest)
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> why can't it find sprintf?

Because you pass libc to the linker before the file that uses it. It 
should come after all your object files in the linker command line.

Author: Andreas B. (Guest)
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That, and you should be using gcc for linking instead of ld directly. 
This will solve a lot of environment issues such as library paths and 
linking of libc.

Your linking of main.out repeats all the dependencies on the command 
line of the linker, use make variable $^ instead. Also, the standard 
variable name for linker flags is LDDFLAGS. Likewise the standard for C 
compiler flags is CFLAGS, not CAFLAGS, and -c shouldn't be in it because 
it is not a flag, it belongs on the command line. That is relevant 
because these names are used in default rules, which you might want to 
mix in. Then you should also explicitly name the output (conveniently 
available in $@) on the command line.

Here is a pattern rule I use for example:
%.o: %.c
        @echo "CC   $@"
        @$(CC) -c -o $@ $(CPPFLAGS) $(CFLAGS) $<
It is basically the default pattern rule modified to hide the command 
line so that warnings and errors are easier to read in the make output.


In your simple.cmd linker script I see that you are putting the 
initialized data sections into the uninitialized data section of the 
output. This is definitely wrong. All your initialized static and global 
variables will start with zero instead of the given value. Even if you 
can handle that it will also break any linked library that makes use of 
initialized data.


Your Makefile is missing all dependency information. All source files 
depend at least on the headers they include and they need to be 
recompiled if any of those changes. You can still use the pattern rules 
to compile and use the initial line of a rule for the dependency 
information. Example:
main.o: main.c someheader.h
other.o: other.c another.h someheader.h
The advanced make user can script some automatic dependency generation 
(that's what gcc's -M flag is for).

Author: Mike P (Guest)
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thank you--that addressed this problem!  now i can see something new 
(see new posting i'll be writing next).

Author: Mike P (Guest)
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>That, and you should be using gcc for linking instead of ld directly.
This will solve a lot of environment issues such as library paths and
linking of libc.

don't know how to change that.  am nervous to make that change since the 
example used something else.  even as a professional developer (delphi), 
i find myself very unprepared for this.

>Your linking of main.out repeats all the dependencies on the command
line of the linker, use make variable $^ instead. Also, the standard
variable name for linker flags is LDDFLAGS. Likewise the standard for C
compiler flags is CFLAGS, not CAFLAGS, and -c shouldn't be in it because
it is not a flag, it belongs on the command line. That is relevant
because these names are used in default rules, which you might want to
mix in. Then you should also explicitly name the output (conveniently
available in $@) on the command line.
>
>Here is a pattern rule I use for example:
>
>%.o: %.c
>        @echo "CC   $@"
>        @$(CC) -c -o $@ $(CPPFLAGS) $(CFLAGS) $<
>
>It is basically the default pattern rule modified to hide the command
line so that warnings and errors are easier to read in the make output.

i'm nervous to change too much because i lack the experience to fix the 
problems that may arise.  have made some of the changes.  once i get 
things compiling, i will be more brave...

>In your simple.cmd linker script I see that you are putting the
initialized data sections into the uninitialized data section of the
output. This is definitely wrong. All your initialized static and global
variables will start with zero instead of the given value. Even if you
can handle that it will also break any linked library that makes use of
initialized data.

i moved "*(.data)" into ".text".  is that the correct solution?

>Your Makefile is missing all dependency information. All source files
depend at least on the headers they include and they need to be
recompiled if any of those changes. You can still use the pattern rules
to compile and use the initial line of a rule for the dependency
information. Example:
>
>main.o: main.c someheader.h
>other.o: other.c another.h someheader.h

i think i have fixed this problem.  can you have another look?

>The advanced make user can script some automatic dependency generation
(that's what gcc's -M flag is for).

i do not fit in that category.

i've attached revised copies.

thank you for all your help!!!

Author: Mike P (Guest)
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got everything working--thank you!!!

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