Need help - Can't run a simple C++ application

Since your workstation is running a more recent glibc, you can't simply install correct libraries on the target (libc, libm and ld-linux all form a "package", and must be upgraded together; you saw what happens when they are not).

Your choices are (in order of increasing difficulty, I think):

- upgrade target to the same version of glibc as that on workstation.

- install a gcc x86 => x86 cross-compiler (details in "info gcc").

- downgrade workstation to the same version of glibc as that on the target (you'll have to find a distribution that used the "old" glibc; simply downgrading glibc by itself will likely render the workstation unusable).

Cheers,

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In order to understand recursion you must first understand recursion.

Or link the program statically (e.g. with the compiler switch "-all-static") and run "strip programname" afterwards. Of course, this is not a good idea if you have more programs as each will become several 100 kbytes larger.

Greetings Ernst

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Ernst,

Eventually I will want to link with shared libraries because I will be developing other applications for the target. Right now I will try to link the program statically, this will allow me to start development right now and give me more time to resolve the shared library issue later.

I tried the compiler switch you suggested, but it errors: # g++ -all-static -o hello.out hello.cpp cc1plus: unrecognized option `-all-static'

So I tried this: # g++ -static -o hello.out hello.cpp /usr/bin/ld: cannot find -lstdc++ collect2: ld returned 1 exit status

I don't know why it does not find libstdc++, I think it's there: # ls /usr/lib/*stdc++* /usr/lib/libstdc++-3-libc6.2-2-2.10.0.so* /usr/lib/libstdc++.so.5@ /usr/lib/libstdc++-libc6.1-1.so.2@ /usr/lib/libstdc++.so.5.0.3* /usr/lib/libstdc++-libc6.2-2.so.3@

Is it because I only have the shared version of the library and not the static version? If so, how do I get the static version?

Thanks for the help.

Eric

Hello Eric,

-all-static seems to work only after the -o flag. I use KDevelop and added # the library search path: myprogram_LDFLAGS = $(all_libraries) -all-static

If I use -all-static on another place (e.g. like in your example) it won't work either.

Yes. you need the *.a or *.o files.

*.a is an archive of *.o files.

maybe here:

If you are using a distribution, it might be on the CD as a separate package. Otherwise, I guess, you have to "make" it from the source. But I have never done this myself. 8-)

Greetings Ernst

PS: I think configuration of the development system is more complicated than programming. 8-)

That's correct.

That depends on which distribution of Linux you are using. If it's rpm-based, you should look for the correct rpm (try

If it's deb-based, look for the correct debian package. If it's neither, download and build the source.

- Adam

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Hello Ernst and Adam,

I finally succeeded in compiling the thing statically.

By reading your replies, I understood that I had to find the static versions of the libraries. I had a look on rpmfind.net and searched for stdc++* and saw the library libstdc++5-static-devel-3.2.2-3mdk.i586.rpm for my Mandrake distribution. I then took a second look at the CDs that I had used for the installation and sure enough, it was there, so I installed it and recompiled. When I saw that the error message had changed and said it could not find libm, I knew I was making progress. I installed the static version of glibc, recompiled and voilà. I now have a whopping

665KB "Hello World" program! Not very compact, but it's a first step. I runs fine on the embedded device.

I simply used the following command: $ g++ -static -o hello.out hello.cpp

I'll post back here later when I'll need to link to the shared libraries, but in the mean time I can start working on my code.

Thank you all for your help.

Eric

I now have a whopping

Even with the strip command? strip would remove unused functions.

greetings ernst

I'd be interested to see how strip does that. How does it know that a function is not used? =46rom the finely printed manual:

strip - Discard symbols from object files.

--

Josef M=F6llers (Pinguinpfleger bei FSC)
	If failure had no penalty success would not be a prize
						-- T.  Pratchett

Josef Möllers writes:

It discards debugging symbols (typically). As you can see below, there are debugging sections of the binary, which strip removes. You can also use it to remove specific sections (not commonly used). This is a ~reasonably large C++ application compiled using GCC 3.3.2. strip removes the DWARF2 debugging symbol tables:

[before strip]

-rwxr-xr-x 1 roger roger 6204796 2003-11-17 15:51 someprog

[objdump -h] someprog: file format elf32-i386

Sections: Idx Name Size VMA LMA File off Algn 0 .interp 00000013 08048114 08048114 00000114 2**0 CONTENTS, ALLOC, LOAD, READONLY, DATA 1 .note.ABI-tag 00000020 08048128 08048128 00000128 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 2 .hash 00002950 08048148 08048148 00000148 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 3 .dynsym 000064b0 0804aa98 0804aa98 00002a98 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 4 .dynstr 00010ab2 08050f48 08050f48 00008f48 2**0 CONTENTS, ALLOC, LOAD, READONLY, DATA 5 .gnu.version 00000c96 080619fa 080619fa 000199fa 2**1 CONTENTS, ALLOC, LOAD, READONLY, DATA 6 .gnu.version_r 00000080 08062690 08062690 0001a690 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 7 .rel.dyn 000001c8 08062710 08062710 0001a710 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 8 .rel.plt 00000f78 080628d8 080628d8 0001a8d8 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 9 .init 00000017 08063850 08063850 0001b850 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 10 .plt 00001f00 08063868 08063868 0001b868 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 11 .text 000446b0 08065770 08065770 0001d770 2**4 CONTENTS, ALLOC, LOAD, READONLY, CODE 12 .fini 0000001b 080a9e20 080a9e20 00061e20 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 13 .rodata 00011a45 080a9e40 080a9e40 00061e40 2**5 CONTENTS, ALLOC, LOAD, READONLY, DATA 14 .eh_frame_hdr 00000fbc 080bb888 080bb888 00073888 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 15 .data 0000000c 080bd844 080bd844 00074844 2**2 CONTENTS, ALLOC, LOAD, DATA 16 .eh_frame 00004774 080bd850 080bd850 00074850 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 17 .gcc_except_table 00007dec 080c1fc4 080c1fc4 00078fc4 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 18 .dynamic 000001a0 080c9db0 080c9db0 00080db0 2**2 CONTENTS, ALLOC, LOAD, DATA 19 .ctors 00000030 080c9f50 080c9f50 00080f50 2**2 CONTENTS, ALLOC, LOAD, DATA 20 .dtors 00000008 080c9f80 080c9f80 00080f80 2**2 CONTENTS, ALLOC, LOAD, DATA 21 .jcr 00000004 080c9f88 080c9f88 00080f88 2**2 CONTENTS, ALLOC, LOAD, DATA 22 .got 000007cc 080c9f8c 080c9f8c 00080f8c 2**2 CONTENTS, ALLOC, LOAD, DATA 23 .bss 000006ec 080ca758 080ca758 00081758 2**3 ALLOC 24 .comment 000002be 00000000 00000000 00081758 2**0 CONTENTS, READONLY 25 .debug_aranges 00000ec0 00000000 00000000 00081a18 2**3 CONTENTS, READONLY, DEBUGGING 26 .debug_pubnames 0000d189 00000000 00000000 000828d8 2**0 CONTENTS, READONLY, DEBUGGING 27 .debug_info 00491b89 00000000 00000000 0008fa61 2**0 CONTENTS, READONLY, DEBUGGING 28 .debug_abbrev 00010f19 00000000 00000000 005215ea 2**0 CONTENTS, READONLY, DEBUGGING 29 .debug_line 0002f652 00000000 00000000 00532503 2**0 CONTENTS, READONLY, DEBUGGING 30 .debug_frame 00005d58 00000000 00000000 00561b58 2**2 CONTENTS, READONLY, DEBUGGING 31 .debug_str 00069d4d 00000000 00000000 005678b0 2**0 CONTENTS, READONLY, DEBUGGING 32 .debug_ranges 00000e48 00000000 00000000 005d15fd 2**0 CONTENTS, READONLY, DEBUGGING

[after strip]

-rwxr-xr-x 1 roger roger 532268 2003-11-18 22:47 someprog

[objdump -h] someprog: file format elf32-i386

Sections: Idx Name Size VMA LMA File off Algn 0 .interp 00000013 08048114 08048114 00000114 2**0 CONTENTS, ALLOC, LOAD, READONLY, DATA 1 .note.ABI-tag 00000020 08048128 08048128 00000128 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 2 .hash 00002950 08048148 08048148 00000148 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 3 .dynsym 000064b0 0804aa98 0804aa98 00002a98 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 4 .dynstr 00010ab2 08050f48 08050f48 00008f48 2**0 CONTENTS, ALLOC, LOAD, READONLY, DATA 5 .gnu.version 00000c96 080619fa 080619fa 000199fa 2**1 CONTENTS, ALLOC, LOAD, READONLY, DATA 6 .gnu.version_r 00000080 08062690 08062690 0001a690 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 7 .rel.dyn 000001c8 08062710 08062710 0001a710 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 8 .rel.plt 00000f78 080628d8 080628d8 0001a8d8 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 9 .init 00000017 08063850 08063850 0001b850 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 10 .plt 00001f00 08063868 08063868 0001b868 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 11 .text 000446b0 08065770 08065770 0001d770 2**4 CONTENTS, ALLOC, LOAD, READONLY, CODE 12 .fini 0000001b 080a9e20 080a9e20 00061e20 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 13 .rodata 00011a45 080a9e40 080a9e40 00061e40 2**5 CONTENTS, ALLOC, LOAD, READONLY, DATA 14 .eh_frame_hdr 00000fbc 080bb888 080bb888 00073888 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 15 .data 0000000c 080bd844 080bd844 00074844 2**2 CONTENTS, ALLOC, LOAD, DATA 16 .eh_frame 00004774 080bd850 080bd850 00074850 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 17 .gcc_except_table 00007dec 080c1fc4 080c1fc4 00078fc4 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA 18 .dynamic 000001a0 080c9db0 080c9db0 00080db0 2**2 CONTENTS, ALLOC, LOAD, DATA 19 .ctors 00000030 080c9f50 080c9f50 00080f50 2**2 CONTENTS, ALLOC, LOAD, DATA 20 .dtors 00000008 080c9f80 080c9f80 00080f80 2**2 CONTENTS, ALLOC, LOAD, DATA 21 .jcr 00000004 080c9f88 080c9f88 00080f88 2**2 CONTENTS, ALLOC, LOAD, DATA 22 .got 000007cc 080c9f8c 080c9f8c 00080f8c 2**2 CONTENTS, ALLOC, LOAD, DATA 23 .bss 000006ec 080ca758 080ca758 00081758 2**3 ALLOC 24 .comment 000002be 00000000 00000000 00081758 2**0 CONTENTS, READONLY

Using readelf -w, I can see the details of the Debian build daemon that built my glibc--a potential security concern?

DW_AT_comp_dir : /build/buildd/glibc-2.3.2.ds1/build-tree/glibc-2.3.2/csu DW_AT_producer : GNU AS 2.14.90.0.7 DW_AT_language : 32769 (MIPS assembler) ^^^^^^^^^^^^^^Huh, I'm using ix86!

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OK, I think I was wrong. according to the man page unused relocation information and debugging symbols are removed. In my case this is 3/4 of the file size.

But why cannot functions be removed (what is unused relocation information)? I could imagine that a segment, where no jump goes to, could be removed.

Greetings Ernst

f the

ion)?

=2E

(I'm not a C++ expert, so I give this example in C): static void f(); main() { void (*p)() =3D &f; (*f)(); } void f(){ printf("Hello, world!\n"); }

No jump to f, but f is not unused. You could make this arbitrarily complex.

As for the "unused relocation information": if you're referring to the "--strip-unneeded" option, the relocation table contains reference to symbols which must be relocated during linking. Those entries in the symbol table which are not referenced in the relocation table can be removed. A quick test on a simple program reveals that gcc2_compiled is one of such symbols.

Josef

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Josef M=F6llers (Pinguinpfleger bei FSC)
	If failure had no penalty success would not be a prize
						-- T.  Pratchett

How does this contradict what I wrote? As you write yourself: it just removes debugging information. All sections which contain CODE are left untouched: =2Einit, .plt, .text, .fini, so no unused functions have been removed.

--

Josef M=F6llers (Pinguinpfleger bei FSC)
	If failure had no penalty success would not be a prize
						-- T.  Pratchett

AFAIK, unused functions are already removed by the linker.

-Michael

The linker removes functions that are not _ referenced _.

They could even be removed by the code generator itself (an unused static function does not need code to be generated). As for the linker, IMHO this would violate the task of the linker. It would re-arrange code within a linkable object. But then, it could do this, because it knows that there is no reference to the function label.

--

Josef M=F6llers (Pinguinpfleger bei FSC)
	If failure had no penalty success would not be a prize
						-- T.  Pratchett

Any sensible linker with some kind of library utility would not include any library routines that are not referenced by the main program or modules needed by the main program.

However, if the execution environment supports dynamic linking (such as xxx.dll or xxx.so files), it would be quite dangerous to remove any globally available symbol (variable or function) from the final image, if the module has been specified on the linker command line, since the linker can not know, if this symbol will ever be referenced by any dynamically loaded function during run time.

Paul

Up to now I never considered dynamic linking and so I don't know what goes on there (but I did watch the GCC linker working for statically linked projects in embedded environments). I suppose you need to tell the linker about the dynamic option.

Does dynamic linking include a jump table to access the referenced functions or do the calls go directly in the midst of the code ?

-Michael

Ernst,

Thanks for reminding me about using strip. It works, it reduced the file size from 664,759 bytes to 420,024 bytes for my "Hello World" test program.

I then tried it on my project executable and the results were more notable, it reduced the file size from 3,753,183 to 852,616 bytes.

Regards,

Eric