Crosstool-NG may generate non-"pure" sysroots

[tpetazzoni]

This is not really an issue per-se, but more a discussion topic.

I've recently encountered a situation where Buildroot got confused because the Crosstool-NG toolchain it was using as an external toolchain containing in its sysroot more than the C library. Indeed, the Crosstool-NG toolchain sysroot also contained the libexpat library, used as a dependency to GDB.

This broke things because:

• Buildroot copies the toolchain sysroot into Buildroot's sysroot (called STAGING_DIR)
• Buildroot packages can discovered that libexpat.so is there, and link with it, while in fact libexpat is not enabled in terms of Buildroot configuration
• Some binaries for the target are linked against libexpat.so, but libexpat.so is not in the target root filesystem, because libexpat is not enabled in terms of Buildroot package

So essentially, the fact that Crosstool-NG generates toolchains that are not "pure" (i.e only contains the C library in their sysroot) causes a problem for build systems that use Crosstool-NG as external toolchains.

I am unclear on what would be the approach to resolve this issue, but I wanted to open the discussion, and see if there are some useful suggestions.

[bhundven]

I am also not sure the best approach to resolving this issue. I would suggest opening this question up on the crossgcc (crossgcc@sourceware.org) mailing list.

[cpackham]

This is because crosstool-ng does carry some extra target packages (gdb, strace & ltrace) an some libraries (I think there's even an open issue wanting zlib for the target). This makes sense for a minimal standalone toolchain but isn't great when the toolchain is a smaller part of a larger package ecosystem like buildroot.

I think what we could do is have a "pure"/"buildroot compatible"/"some other name" kconfig option that disables the target packages. Or perhaps it's just a documentation thing that when building a toolchain for use with buildroot don't enable gdb/strace/other packages provided by buildroot.

[tpetazzoni]

Indeed, I also thought of an explicit option "please generate a toolchain that is just a toolchain". Another possibility is perhaps installing those libraries in another place than the toolchain sysroot ? But I'm not sure how that would work really.