ar86 doesn't recognise object files produced by as86 #16

tlid commented 2026年04月25日 23:58:56 +02:00

dev86 commit: 2f41e7dd02
host machine: 6.12.74+deb13+1-amd64

I'm currently trying to set up a cross-compiler toolchain to allow me to build the MINIX 1 tree, targeting an 8088 XT, on a modern x86-64 machine. I've run into some issues when trying to create a library with ar86. Here's a minimal example:

TOOLS_DIR=~/dev86/bin
CC=$TOOLS_DIR/bcc
AS=$TOOLS_DIR/as86
AR=$TOOLS_DIR/ar86
SOURCE=./foo.c
AS_OUT=./foo.s
OBJ_OUT=./foo.o
LIBFILE=./libfoo.a
cat << EOF > $SOURCE
int foo(void) {
 return 42;
}
EOF
$CC -0 -S -ansi $SOURCE -o $AS_OUT
$AS -0 -o $OBJ_OUT $AS_OUT
rm -f $LIBFILE
$AR r $LIBFILE $OBJ_OUT
echo "adding symbol index"
$AR s $LIBFILE

It produces the following output, throwing an error when trying to add the symbol index to the archive:

$ bash run.sh 
Creating archive file `./libfoo.a'
adding symbol index
~/dev86/bin/ar86: bad format (not an object file) in ./libfoo.a(foo.o)

I will continue to look further into this and don't mind submitting a patch if needed, but any help/ideas would be appreciated

dev86 commit: 2f41e7dd020dd0997bad64094ad8e416ea5ad1ad host machine: 6.12.74+deb13+1-amd64 I'm currently trying to set up a cross-compiler toolchain to allow me to build the MINIX 1 tree, targeting an 8088 XT, on a modern x86-64 machine. I've run into some issues when trying to create a library with `ar86`. Here's a minimal example: ```bash TOOLS_DIR=~/dev86/bin CC=$TOOLS_DIR/bcc AS=$TOOLS_DIR/as86 AR=$TOOLS_DIR/ar86 SOURCE=./foo.c AS_OUT=./foo.s OBJ_OUT=./foo.o LIBFILE=./libfoo.a cat << EOF > $SOURCE int foo(void) { return 42; } EOF $CC -0 -S -ansi $SOURCE -o $AS_OUT $AS -0 -o $OBJ_OUT $AS_OUT rm -f $LIBFILE $AR r $LIBFILE $OBJ_OUT echo "adding symbol index" $AR s $LIBFILE ``` It produces the following output, throwing an error when trying to add the symbol index to the archive: ``` $ bash run.sh Creating archive file `./libfoo.a' adding symbol index ~/dev86/bin/ar86: bad format (not an object file) in ./libfoo.a(foo.o) ``` I will continue to look further into this and don't mind submitting a patch if needed, but any help/ideas would be appreciated

tlid commented 2026年04月28日 00:27:34 +02:00

I originally looked into this because I thought that ld86 was a single-pass linker, turns out it's a two-pass linker. Since it builds a full symbol table at link time, there doesn't appear to be a need to embed a symbol table in the archive. We can just build archives without the -s modifier. I confirmed in a test example that linking is successful irrespective of the order I place objects in a library, even without an index in the archive.

Would be nice to know why the error above occurs though. From looking through the code it appears that, when adding a symbol table, ar86 expects member headers to be in the a.out format rather than the object file headers generated by as86. What's the reason for this?

I originally looked into this because I thought that `ld86` was a single-pass linker, turns out [it's a two-pass linker](https://codeberg.org/jbruchon/dev86/src/commit/2f41e7dd020dd0997bad64094ad8e416ea5ad1ad/ld/readobj.c#L14-L18). Since it builds a full symbol table at link time, there doesn't appear to be a need to embed a symbol table in the archive. We can just build archives without the `-s` modifier. I confirmed in a test example that linking is successful irrespective of the order I place objects in a library, even without an index in the archive. Would be nice to know why the error above occurs though. From looking through the code it appears that, when adding a symbol table, `ar86` expects member headers to be in the `a.out` format rather than the object file headers generated by `as86`. What's the reason for this?