Writing first c program in vi editor in cygwin - c

I [extremely] new to c programming and cygwin so thanks for being patient. I am using a PDF of Michael Vine's C programming for beginners and trying to enter and compile the first example.
Here is what i wrote in vi:
#include <stdio.h>
main ()
{
printf("\nHello World\n");
}
When I try to compile using gcc, I get two errors:
1) usr/lib/gcc/i686-pc-cygwin/3.4.4./... /bin/ld:new: file format not recognized; treating as linked script
2) [same path as above]/bin/ld:new:11: syntax error collect2: ld returned 1 exit status
I'm pretty sure the actual syntax I used in vi is correct (its straight out of an example) and the gcc command is also correct. Am I missing a package or is my path to cygwin screwed up? Anyone know what's going on with this?

GCC, for better or for worse, uses the filename you pass to it to figure out what operation to do - run the compiler, the assembler, or the linker, or some combination, for example. Since you named your source file new, GCC is assuming it's a compiled object and is trying to link it. Either rename it new.c or pass the -x c flag when compiling.
For future reference, a good way to debug funny business with the GCC compiler driver is to pass the -v flag. If you do so for your original command line you'll see that it just invokes the linker, skipping the compilation step. An example from my machine:
$ gcc -v new -o new.exe
Using built-in specs.
Target: i686-apple-darwin11
Configured with: /private/var/tmp/llvmgcc42/llvmgcc42-2336.11~182/src/configure --disable-checking --enable-werror --prefix=/Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2 --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-prefix=llvm- --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin11 --enable-llvm=/private/var/tmp/llvmgcc42/llvmgcc42-2336.11~182/dst-llvmCore/Developer/usr/local --program-prefix=i686-apple-darwin11- --host=x86_64-apple-darwin11 --target=i686-apple-darwin11 --with-gxx-include-dir=/usr/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)
/usr/llvm-gcc-4.2/bin/../libexec/gcc/i686-apple-darwin11/4.2.1/collect2 -dynamic -arch x86_64 -macosx_version_min 10.8.4 -weak_reference_mismatches non-weak -o new.exe -lcrt1.10.6.o -L/usr/llvm-gcc-4.2/bin/../lib/gcc/i686-apple-darwin11/4.2.1/x86_64 -L/Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2/lib/gcc/i686-apple-darwin11/4.2.1/x86_64 -L/usr/llvm-gcc-4.2/bin/../lib/gcc/i686-apple-darwin11/4.2.1 -L/usr/llvm-gcc-4.2/bin/../lib/gcc -L/Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2/lib/gcc/i686-apple-darwin11/4.2.1 -L/usr/llvm-gcc-4.2/bin/../lib/gcc/i686-apple-darwin11/4.2.1/../../.. -L/Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2/lib/gcc/i686-apple-darwin11/4.2.1/../../.. new -lSystem -lgcc -lSystem
ld: warning: ignoring file new, file was built for unsupported file format ( 0x20 0x23 0x69 0x6e 0x63 0x6c 0x75 0x64 0x65 0x20 0x3c 0x73 0x74 0x64 0x69 0x6f ) which is not the architecture being linked (x86_64): new
Undefined symbols for architecture x86_64:
"_main", referenced from:
start in crt1.10.6.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

One basic syntax error:
' main(){ ... } '
In C/C++, your main function should be:
'int main(){ ... }'

Related

Is it posible to compile Flex/Lex on a M1 Mac

In my compilers class we are writting Flex/Lex code. When I compiled the .l file and tried to compile the resultant lex.yy.c file with gcc, I got the following error:
Undefined symbols for architecture arm64:
"_yywrap", referenced from:
_yylex in lex-fb85c9.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Does is posible to compile it in a Apple Silicon (M1) Mac, at least in a Linux VM?
I created a test file and compiled:
% flex lex.l
% cc -o lex lex.yy.c -lc -ll
% grep 'yylex();' lex.yy.c
yylex();
The -ll on the cc command links against the libl library. Current M1 based macOS does not provide a libfl library you may see referenced.

Undefined symbols for architecture arm64: `"_puts"`

I am writing a simple "Hello world" program using MacBook Air 2020 (M1) and the C code is as follows:
#include<stdio.h>
int main(void){
printf("Hello world!\n");
return 0;
}
clang version is
Apple clang version 14.0.0 (clang-1400.0.29.201)
Target: arm64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
However after I compiled it and try to run ld hello.o -o hello it gives the following error:
Undefined symbols for architecture arm64:
"_puts", referenced from:
_main in hello.o
ld: symbol(s) not found for architecture arm64
Why is the symbol not defined?
Link using the compiler (clang hello.o -o hello) — it will add the standard C library and the startup code, etc to the ld command line.
Add -v to the options to see what the compiler actually executes.
On an Intel Mac running macOS Big Sur 11.7, part of the information produced was this humungous long line which invokes the loader (ld) in a ridiculously obscure location:
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -lto_library /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -platform_version macos 11.0.0 12.1 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -o tm59 -L/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib -L/usr/local/lib /var/folders/sj/_v4_1hp947d_6qg_m75syr000000gn/T/tm59-7bf6b1.o -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/13.0.0/lib/darwin/libclang_rt.osx.a

When using the GCC driver, what makes a static lib "incompatible"?

So what I am trying to do is on Ubuntu 14.04 (x86_64) I want to set up musl-libc based on the latest released 1.1.11 version which is available at this moment.
What I did was to:
Install multilib support for GCC: sudo apt-get --no-install-recommends install gcc-multilib
Configure the libraries for 32-bit and 64-bit respectively and install them into separate folders:
CFLAGS=-m32 ./configure --prefix=$HOME/bin/musl-32-bit --disable-shared --target=i386-linux-gnu && make && make install
CFLAGS=-m64 ./configure --prefix=$HOME/bin/musl-64-bit --disable-shared --target=x86_64-linux-gnu
Then in order to build a statically linked premake4, I invoke GNU make like this on the Makefile generated by premake4:
make -j 8 CC=$HOME/bin/musl-32-bit/bin/musl-gcc ARCH=-m32 LDFLAGS="-v -static" verbose=1
This appears to work up to the linking step, which bombs with:
Linking Premake4
$HOME/bin/musl-32-bit/bin/musl-gcc -o bin/release/premake4 intermediate/gmake__/premake.o intermediate/gmake__/os_uuid.o intermediate/gmake__/os_pathsearch.o intermediate/gmake__/os_match.o intermediate/gmake__/os_chdir.o intermediate/gmake__/os_mkdir.o intermediate/gmake__/os_stat.o intermediate/gmake__/os_getversion.o intermediate/gmake__/premake_main.o intermediate/gmake__/os_isdir.o intermediate/gmake__/string_endswith.o intermediate/gmake__/os_isfile.o intermediate/gmake__/scripts.o intermediate/gmake__/path_isabsolute.o intermediate/gmake__/os_rmdir.o intermediate/gmake__/os_getcwd.o intermediate/gmake__/os_is64bit.o intermediate/gmake__/os_copyfile.o intermediate/gmake__/lstate.o intermediate/gmake__/ltable.o intermediate/gmake__/lgc.o intermediate/gmake__/lobject.o intermediate/gmake__/lcode.o intermediate/gmake__/lmathlib.o intermediate/gmake__/lbaselib.o intermediate/gmake__/lmem.o intermediate/gmake__/lfunc.o intermediate/gmake__/lparser.o intermediate/gmake__/ldblib.o intermediate/gmake__/lzio.o intermediate/gmake__/lstrlib.o intermediate/gmake__/lvm.o intermediate/gmake__/lauxlib.o intermediate/gmake__/llex.o intermediate/gmake__/lstring.o intermediate/gmake__/ldump.o intermediate/gmake__/ldebug.o intermediate/gmake__/loadlib.o intermediate/gmake__/lopcodes.o intermediate/gmake__/linit.o intermediate/gmake__/ldo.o intermediate/gmake__/lapi.o intermediate/gmake__/liolib.o intermediate/gmake__/loslib.o intermediate/gmake__/lundump.o intermediate/gmake__/ltm.o intermediate/gmake__/ltablib.o -v -static -L. -s -rdynamic -lm -ldl
Using built-in specs.
Reading specs from $HOME/bin/musl-32-bit/lib/musl-gcc.specs
rename spec cpp_options to old_cpp_options
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.4-2ubuntu1~14.04' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04)
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../lib32/:/lib/../lib32/:/usr/lib/../lib32/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-m32' '-o' 'bin/release/premake4' '-v' '-static' '-L.' '-s' '-rdynamic' '-specs=$HOME/bin/musl-32-bit/lib/musl-gcc.specs' '-mtune=generic' '-march=i686'
/usr/lib/gcc/x86_64-linux-gnu/4.8/collect2 -dynamic-linker /lib/ld-musl-i386.so.1 -nostdlib -static -export-dynamic -z relro -o bin/release/premake4 -s $HOME/bin/musl-32-bit/lib/crt1.o $HOME/bin/musl-32-bit/lib/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.8/crtbegin.o -L. -L$HOME/bin/musl-32-bit/lib -L /usr/lib/gcc/x86_64-linux-gnu/4.8/. intermediate/gmake__/premake.o intermediate/gmake__/os_uuid.o intermediate/gmake__/os_pathsearch.o intermediate/gmake__/os_match.o intermediate/gmake__/os_chdir.o intermediate/gmake__/os_mkdir.o intermediate/gmake__/os_stat.o intermediate/gmake__/os_getversion.o intermediate/gmake__/premake_main.o intermediate/gmake__/os_isdir.o intermediate/gmake__/string_endswith.o intermediate/gmake__/os_isfile.o intermediate/gmake__/scripts.o intermediate/gmake__/path_isabsolute.o intermediate/gmake__/os_rmdir.o intermediate/gmake__/os_getcwd.o intermediate/gmake__/os_is64bit.o intermediate/gmake__/os_copyfile.o intermediate/gmake__/lstate.o intermediate/gmake__/ltable.o intermediate/gmake__/lgc.o intermediate/gmake__/lobject.o intermediate/gmake__/lcode.o intermediate/gmake__/lmathlib.o intermediate/gmake__/lbaselib.o intermediate/gmake__/lmem.o intermediate/gmake__/lfunc.o intermediate/gmake__/lparser.o intermediate/gmake__/ldblib.o intermediate/gmake__/lzio.o intermediate/gmake__/lstrlib.o intermediate/gmake__/lvm.o intermediate/gmake__/lauxlib.o intermediate/gmake__/llex.o intermediate/gmake__/lstring.o intermediate/gmake__/ldump.o intermediate/gmake__/ldebug.o intermediate/gmake__/loadlib.o intermediate/gmake__/lopcodes.o intermediate/gmake__/linit.o intermediate/gmake__/ldo.o intermediate/gmake__/lapi.o intermediate/gmake__/liolib.o intermediate/gmake__/loslib.o intermediate/gmake__/lundump.o intermediate/gmake__/ltm.o intermediate/gmake__/ltablib.o -lm -ldl --start-group /usr/lib/gcc/x86_64-linux-gnu/4.8/libgcc.a /usr/lib/gcc/x86_64-linux-gnu/4.8/libgcc_eh.a -lc --end-group /usr/lib/gcc/x86_64-linux-gnu/4.8/crtend.o $HOME/bin/musl-32-bit/lib/crtn.o
/usr/bin/ld: skipping incompatible $HOME/bin/musl-32-bit/lib/libc.a when searching for -lc
/usr/bin/ld: cannot find -lc
collect2: error: ld returned 1 exit status
make[1]: *** [bin/release/premake4] Error 1
make: *** [Premake4] Error 2
The relevant line is:
/usr/bin/ld: skipping incompatible $HOME/bin/musl-32-bit/lib/libc.a when searching for -lc
Now the part I don't understand about this is, that when I ar x the libc.a (into a folder $HOME/bin/musl-32-bit/lib/libc) generated during the build step of musl-libc (see above), it proves that all of the objects included seem to be of the correct target architecture (all show ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped) as I can prove from coming up empty when issuing the following command:
find $HOME/bin/musl-32-bit/lib -name '*.o' -exec file {} +|grep -v 'ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped'
And in fact this gives no output. Similarly when looking inside the build directory using the same method, I cannot find any object file that doesn't match my expectation.
For good measure I decided to also task objdump to tell me more about the libc.a in question and came up with the same result:
objdump -a $HOME/bin/musl-32-bit/lib/libc.a|grep 'file format'|grep -v 'file format elf32-i386'
So my question is twofold:
what disqualifies a static library as "incompatible" when GCC is asked to link it?
what could be the particular issue I am seeing?
The first is what I am really interested in, but with the second I am asking to share your experience with trouble-shooting like this. Which verification steps have I missed, for example?
Please note that the "native" premake4 builds just fine with:
make -j 8 CC=$HOME/bin/musl-64-bit/bin/musl-gcc ARCH=-m64 LDFLAGS=-static verbose=1
From the output when adding the -v flag to LDFLAGS it appears as if the target always stays at x86_64-linux-gnu. I have yet to come up with a method to fix this, though.
In short, the musl-gcc wrapper script setup is not well-suited to use with -m32. I think what's happening is that the actual compiler is getting invoked in the default (64-bit) mode by musl-gcc, then the resulting object files are not compatible with the (intended, 32-bit) libc.
It may work if you put -m32 in the generated wrapper script. This will happen automatically with recent versions if you put the -m32 in $CC (i.e. CC="gcc -m32") rather than putting it in $CFLAGS.
Update: As noted in the discussion that was moved to chat, adding -Wl,-melf_i386 is probably also needed (due to flaws in the spec file used by the musl-gcc wrapper that don't account for -m32 support) but still does not seem to be sufficient.
The solution
It turns out the solution is rather simple.
We need to tell both the linker and the driver to use -m32 ... I was that far before. However, it turns out that the missing piece was to pass the linker option to the driver via CFLAGS like this -Wl,-melf_i386.
I am finally able to build and link the 32-bit executable on a multilib-enabled 64-bit host.
NB: Below information is left in place for those who want to learn how I investigated the issue.
Alright, so I investigated the issue a little further and the output gets more enlightening once you extract the object files. To reproduce what I am doing you may have to use Bash or a similar shell that allows for $(...) or you need to adjust the command lines accordingly.
First off it's important to have gcc-multilib and friends installed in order to target -m32 (i386-linux-gnu which happens to be an alias for i686-linux-gnu here).
The code and the make file
I had the following make file:
CC?=$(HOME)/bin/musl/bin64/musl-gcc
BLDARCH?=-m64
CFLAGS+=-v $(BLDARCH)
LDFLAGS+=-v -static $(BLDARCH)
all: helloworld
helloworld: helloworld.c
clean:
rm -f helloworld
rebuild: clean all
.PHONY: clean rebuild
.NOTPARALLEL: rebuild
and the following small helloworld.c:
#include <stdio.h>
int main(int argc, char** argv)
{
printf("Hello world!\n");
return 0;
}
and my 32-bit musl-libc was installed to $HOME/bin/musl/{bin,include,lib}32 respectively. The 64-bit one was installed to $HOME/bin/musl/{bin,include,lib}64 respectively.
Attempting to build with:
make CC=$HOME/bin/musl/bin32/musl-gcc BLDARCH=-m32 rebuild
always failed with the same meaningless lines:
/usr/bin/ld: skipping incompatible ~/bin/musl/lib32/libc.a when searching for -lc
/usr/bin/ld: cannot find -lc
collect2: error: ld returned 1 exit status
make: *** [helloworld] Error 1
Digging into the details
So after some contemplation I decided to re-do the steps done by the gcc driver manually.
This meant to run roughly (I replaced all occurrences of my home folder with a ~):
Compile: /usr/lib/gcc/x86_64-linux-gnu/4.8/cc1 -quiet -imultilib 32 -imultiarch i386-linux-gnu helloworld.c -nostdinc -isystem ~/bin/musl/include32 -isystem /usr/lib/gcc/x86_64-linux-gnu/4.8/include -quiet -dumpbase helloworld.c -m32 -mtune=generic -march=i686 -auxbase helloworld -version -fstack-protector -Wformat -Wformat-security -o /tmp/ccGmMuR1.s
Assemble: as -v -v --32 -o /tmp/ccgRGlqf.o /tmp/ccGmMuR1.s
Link: env COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/ LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/32/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../lib32/:/lib/../lib32/:/usr/lib/../lib32/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../:/lib/:/usr/lib/ COLLECT_GCC_OPTIONS="-v -v -static -m32 -o helloworld -specs=~/bin/musl/lib32/musl-gcc.specs -mtune=generic -march=i686" /usr/lib/gcc/x86_64-linux-gnu/4.8/collect2 -dynamic-linker /lib/ld-musl-i386.so.1 -nostdlib -static -z relro -o helloworld ~/bin/musl/lib32/crt1.o ~/bin/musl/lib32/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.8/32/crtbegin.o -L~/bin/musl/lib32 -L /usr/lib/gcc/x86_64-linux-gnu/4.8/32/. /tmp/ccpL09mJ.o --start-group /usr/lib/gcc/x86_64-linux-gnu/4.8/32/libgcc.a /usr/lib/gcc/x86_64-linux-gnu/4.8/32/libgcc_eh.a -lc --end-group /usr/lib/gcc/x86_64-linux-gnu/4.8/32/crtend.o ~/bin/musl/lib32/crtn.o
Obviously this didn't change the error message a bit just yet:
/usr/bin/ld: skipping incompatible ~/bin/musl/lib32/libc.a when searching for -lc
/usr/bin/ld: cannot find -lc
collect2: error: ld returned 1 exit status
So I took out the -lc from the command line for collect2 and created a folder ~/bin/musl/lib32/archive into which I extracted the whole libc.a generated by my musl-libc build attempt. I then instructed collect2 where to find the object files like this:
Link: env COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/ LIBRARY_PATH=/usr/lib/gc
c/x86_64-linux-gnu/4.8/32/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../lib32/:/lib/../lib32/:/usr/lib/../lib32/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../:/lib/:/usr/lib/ COLLECT_GCC_OPTIONS="-v -v -
static -m32 -o helloworld -specs=~/bin/musl/lib32/musl-gcc.specs -mtune=generic -march=i686" /usr/lib/gcc/x86_64-linux-gnu/4.8/collect2 -dynamic-linker /lib/ld-musl-i386.so.1 -nostdlib -static -z relro -o helloworld $HOME/bin/musl/lib32/crt1.o ~/bin/musl/lib32/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.8/32/crtbegin.o -L~/bin/musl/lib32 -L /usr/lib/gcc/x86_64-linux-gnu/4.8/32/. /tmp/ccpL09mJ.o --start-group /usr/lib/gcc/x86_64-linux-g
nu/4.8/32/libgcc.a /usr/lib/gcc/x86_64-linux-gnu/4.8/32/libgcc_eh.a --end-group /usr/lib/gcc/x86_64-linux-gnu/4.8/32/crtend.o ~/bin/musl/lib32/crtn.o $(find ~/bin/musl/lib32/archive -type f -name '*.o')
This gist is taking out -lc and appending $(find ~/bin/musl/lib32/archive -type f -name '*.o').
Which gave me a whole bunch of new, but more meaningful errors similar to the following ones:
/usr/bin/ld: Warning: size of symbol `__init_ssp' changed from 1 in ~/bin/musl/lib32/archive/__libc_start_main.o to 65 in ~/bin/musl/lib32/archive/__stack_chk_fail.o
/usr/bin/ld: Warning: size of symbol `__funcs_on_exit' changed from 126 in ~/bin/musl/lib32/archive/atexit.o to 1 in ~/bin/musl/lib32/archive/exit.o
# more of those
/usr/bin/ld: i386 architecture of input file `~/bin/musl/lib32/crt1.o' is incompatible with i386:x86-64 output
/usr/bin/ld: i386 architecture of input file `~/bin/musl/lib32/crti.o' is incompatible with i386:x86-64 output
# more of those
The plot thickens. Apparently the collect2 command gets the wrong idea about what to build. Which is odd considering the output for the governing environment variables:
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/32/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../lib32/:/lib/../lib32/:/usr/lib/../lib32/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-v' '-static' '-m32' '-o' 'helloworld' '-specs=~/bin/musl/lib32/musl-gcc.specs' '-mtune=generic' '-march=i686'
... which I passed using env in my attempt to reproduce the conditions encountered by the collect2 wrapper when linking the libc.a.
In order to find out more about the internals of the GNU compilers one needs to read https://gcc.gnu.org/onlinedocs/gccint/
Unfortunately the part about collect2 doesn't help us here. But the lengthy output of /usr/lib/gcc/x86_64-linux-gnu/4.8/collect2 --help looks promising.
Just how could we smuggle our command line option to collect2?
For now I was going to settle for whatever I could run manually. So I attempted to tell the linker which output format I expected. Based on the list of supported targets I was interested in elf_i386.
Passing -melf_386 at the end of the previous line gave an interesting error output. Numerous referenced functions such as __vsyscall, __moddi3 and __divdi3 were undefined. That indicated they simply didn't exist in the object files from the static lib or in any of the startup .o files for that matter:
~/bin/musl/lib32/archive/aio.o: In function `cleanup':
aio.c:(.text+0x5ad): undefined reference to `__vsyscall'
aio.c:(.text+0x5bb): undefined reference to `__vsyscall'
aio.c:(.text+0x5e8): undefined reference to `__vsyscall'
aio.c:(.text+0x5f6): undefined reference to `__vsyscall'
aio.c:(.text+0x61d): undefined reference to `__vsyscall'
~/bin/musl/lib32/archive/aio.o:aio.c:(.text+0x62b): more undefined references to `__vsyscall' follow
~/bin/musl/lib32/archive/cpow.o: In function `cpow':
cpow.c:(.text+0x4f): undefined reference to `__mulxc3'
~/bin/musl/lib32/archive/cpowf.o: In function `cpowf':
cpowf.c:(.text+0x47): undefined reference to `__mulxc3'
~/bin/musl/lib32/archive/cpowl.o: In function `cpowl':
cpowl.c:(.text+0x4c): undefined reference to `__mulxc3'
~/bin/musl/lib32/archive/sysconf.o: In function `sysconf':
sysconf.c:(.text+0xcc): undefined reference to `__vsyscall'
~/bin/musl/lib32/archive/__getdents.o: In function `__getdents':
__getdents.c:(.text+0x13): undefined reference to `__vsyscall'
~/bin/musl/lib32/archive/opendir.o: In function `opendir':
opendir.c:(.text+0x37): undefined reference to `__vsyscall'
~/bin/musl/lib32/archive/readdir.o: In function `readdir':
readdir.c:(.text+0x1f): undefined reference to `__vsyscall'
~/bin/musl/lib32/archive/__init_tls.o: In function `__init_tls':
__init_tls.c:(.text+0x136): undefined reference to `__vsyscall6'
__init_tls.c:(.text+0x16e): undefined reference to `__vsyscall'
As I had already clarified in my question, the object files from the archive all stated that they were elf32-i386.
The functions __vsyscall and __vsyscall6 should end up in a file called syscall.o given the source file for i386 in musl-libc: src/internal/i386/syscall.s. Let's verify that first. Since there is also a file src/misc/syscall.c the name might be different though. Four files have syscall in the file name:
__syscall_cp.o
syscall_cp.o
syscall.o
syscall_ret.o
Querying those files using nm gave:
$ nm -s $(ls |grep syscall)
__syscall_cp.o:
00000000 t sccp
U __syscall
00000005 T __syscall_cp
00000000 W __syscall_cp_c
syscall_cp.o:
U __cancel
00000008 T __cp_begin
00000035 T __cp_cancel
00000030 T __cp_end
00000000 T __syscall_cp_asm
syscall.o:
00000000 T syscall
U __syscall_ret
U __vsyscall6
syscall_ret.o:
U __errno_location
00000000 T __syscall_ret
Symbols with the symbol type U are undefined and therefore expected by the linker to come from outside (external to each object file).
A final $ nm --defined-only *.o ../*.o|grep vsyscall was what was needed to verify that those symbols were indeed missing from the libc.a.
So the cross-built libc.a what was faulty after all. Back to the drawing board.
I hope this description helps others to figure out similar issues and look behind the scenes in GCC.
The saga continues
I was really surprised to see:
$ nm --defined-only ../libc.a |grep -B 2 vsyscall
syscall.o:
0000004b T __syscall
00000000 T __vsyscall
00000031 T __vsyscall6
but for the extracted object files the corresponding command (nm --defined-only *.o ../*.o|grep -B 2 vsyscall) would yield no output.
So inside the libc.a somehow nm sees the two symbols, but after extracting them they disappear? Odd.
Let's look for syscall.o in the libc.a:
$ nm ../libc.a |grep ^syscall
syscall.o:
syscall_ret.o:
syscall.o:
syscall_cp.o:
Whoa? So syscall.o exists twice inside the static library? Well that looks like it may just be the error cause we're looking for. And it certainly does explain why the symbols disappear. Likely the latter syscall.o overwrites the one first extracted when running ar x ....
Confirming:
$ nm ../libc.a |grep -A 4 ^syscall\.o
syscall.o:
0000004b T __syscall
U __sysinfo
00000000 T __vsyscall
00000031 T __vsyscall6
--
syscall.o:
00000000 T syscall
U __syscall_ret
U __vsyscall6
and looking into the musl-libc source tree after doing the 32-bit build:
$ find . -type f -name 'syscall.o' -exec nm {} +
./src/internal/syscall.o:
0000004b T __syscall
U __sysinfo
00000000 T __vsyscall
00000031 T __vsyscall6
./src/misc/syscall.o:
00000000 T syscall
U __syscall_ret
U __vsyscall6
Copying the former into the lib32/archive directory under a name that doesn't collide with existing names gives more errors on other functions, suggesting other object files may also exist as duplicates inside the generated libc.a.
Which ones are duplicates?
$ diff <(nm libc.a|grep ':$'|cut -f 1 -d :|sort) <(nm libc.a|grep ':$'|cut -f 1 -d :|sort -u)
--- /dev/fd/63 2015-10-05 23:58:53.683804823 +0000
+++ /dev/fd/62 2015-10-05 23:58:53.683804823 +0000
## -131,7 +131,6 ##
clogl.o
clog.o
clone.o
-clone.o
closedir.o
close.o
cnd_broadcast.o
## -1115,7 +1114,6 ##
__syscall_cp.o
syscall_cp.o
syscall.o
-syscall.o
syscall_ret.o
sysconf.o
sysinfo.o
This way we see clone.o and syscall.o are affected as duplicates. Which indicates that some object files are missing altogether from the libc.a given undefined references to the following symbols:
__divdi3
__moddi3
__mulxc3
__tls_get_new
__udivdi3
__umoddi3
These names happen to coincide with the ones from the Integer library routines listed for GCC. Which makes me think I am missing one library provided by GCC which to link. Like libgcc?! ...
I have package lib32gcc-4.8-dev which means I should have the required file:
$ apt-file list lib32gcc-4.8-dev|grep -E 'libgcc.*\.a'
lib32gcc-4.8-dev: /usr/lib/gcc/x86_64-linux-gnu/4.8/32/libgcc.a
lib32gcc-4.8-dev: /usr/lib/gcc/x86_64-linux-gnu/4.8/32/libgcc_eh.a
After the previous step I decided to set up a x86_32 version on Ubuntu 14.04 that was essentially at the same patch level.
I then compared the libgcc.a from the x86_32 machine with that from the x86_64 machine. They turned out to be almost identical except for the "symbol value" (in nm lingo) of a handful of functions.
Also, since the symbols were in the static library I attempted to link against the static library again. This worked only with -melf_i386 on the linker (collect2) command line.
After trying to use LDFLAGS and noticing that those were also passed to cc1, I set appended -Wl,-melf_i386 to the CFLAGS and now it worked. Brilliant.
As a side-note: I also swapped the /usr/lib/gcc/x86_64-linux-gnu/4.8/collect2 in the command line for ld of which collect2 is supposed to be a wrapper. The error output was identical.

Trouble debugging C program in Eclipse on Yosemite

I am getting the following persistent errors trying to debug a C program in Eclipse Juno on my mac:
Building target: TimeStamps
Invoking: MacOS X C Linker
gcc -v -o "TimeStamps" ./graphic/arrow.o ./graphic/axesdraw.o . . .
Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.1.0
Thread model: posix
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -dynamic -arch x86_64 -macosx_version_min 10.10.0 -o
Undefined symbols for architecture x86_64:
"_main", referenced from:
implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [TimeStamps] Error 1
So, I am confused about how to fix this in Eclipse. The main routing is in timestamp_test.c
I have -g -v as compiler flags, and -v as a linker flag.
No .o files are made.
Based on the the error given, you need to add the main function to timestamp_test.c.
Or pass the file that have the main function implemented to the compiler.

Macosx, C and embedded lua

Ok, what we have:
Program written on C which compiling and running without problems in Linux and MacOSX (leopard).
I embedded lua code today. Linux: compiled lua 5.1 from source. Everything works and compiles without any problems. Macos: compiled the same lua 5.1 package.
Linked with --llua.
Started compile and got an error:
CC=gcc-4.0 make
ld: warning: in /usr/local/lib/liblua.a, file is not of required architecture
Also tried reinstall, complete remove and installing from macports. The same.
So is there any fix for that?
The error "file is not of required architecture" hints to the fact that you're trying to mix architectures.
Check the architecture of the /usr/local/lib/liblua.a and make sure it matches the architecture or the object you're trying to build.
E.g.
We have a i386 object:
==== cat fun.c ====
#include <stdio.h>
void fun()
{
printf("%s", "foobar\n");
}
gcc -arch i386 -c fun.c -o fun.o
if we try to use it when compiling a x86_64 object (default architecture in Mac OS X):
===== cat test.c ==
extern void fun();
int main()
{
fun();
}
we get:
$ gcc test.c fun.o
ld: warning: ignoring file fun.o, file was built for i386 which is not the architecture being linked (x86_64)
Undefined symbols for architecture x86_64:
"_fun", referenced from:
_main in ccXVCQhG.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

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