[Buildroot] Building cargo with per-package directories

[Buildroot] Building cargo with per-package directories

[Thomas Petazzoni]

Hello ?ric,

As you probably know, I'm working on support for per-package
directories, which will allow to do top-level parallel in a reliable
way. As part of this effort, I've started an autobuilder that uses
per-package directories, and one of the package that is failing a lot
is host-cargo.

It fails like this:

  = note: /usr/bin/ld: cannot find -lhttp_parser
          collect2: error: ld returned 1 exit status
          
error: aborting due to previous error
error: Could not compile `cargo`.

The problem is that while libhttp_parser gets built properly, cargo is
not passing the appropriate -L flag to cargo's per-package host/lib
directory. So the linker doesn't find the libhttp_parser library, and
bails out.

I've tried to look into this, but really the cargo build system is very
unique and weird, and I'm having a hard time finding my way. Do you
think you could help me a bit on this topic ?

To reproduce, you need a machine where libhttp_parser is not installed
system-wide (so either remove it from your system, or build in a
chroot/docker/VM). Then, take this branch:

  https://git.bootlin.com/users/thomas-petazzoni/buildroot/log/?h=ppsh-v7-work

And build the following defconfig:

BR2_arm=y
BR2_cortex_a9=y
BR2_ARM_ENABLE_VFP=y
BR2_PER_PACKAGE_DIRECTORIES=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-arm-cortex-a9-glibc-2018.05.tar.bz2"
BR2_TOOLCHAIN_EXTERNAL_GCC_7=y
BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_16=y
BR2_TOOLCHAIN_EXTERNAL_CUSTOM_GLIBC=y
BR2_TOOLCHAIN_EXTERNAL_CXX=y
BR2_INIT_NONE=y
BR2_SYSTEM_BIN_SH_NONE=y
# BR2_PACKAGE_BUSYBOX is not set
# BR2_TARGET_ROOTFS_TAR is not set
BR2_PACKAGE_HOST_CARGO=y

You should get this failure:

  http://code.bulix.org/fxjgrv-520980?raw

Thanks in advance for your support,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[Buildroot] Building cargo with per-package directories

[Eric Le Bihan]

Hi!
On 2018-12-11 17:12, Thomas Petazzoni wrote:
> Hello ?ric,
>
> As you probably know, I'm working on support for per-package
> directories, which will allow to do top-level parallel in a reliable
> way. As part of this effort, I've started an autobuilder that uses
> per-package directories, and one of the package that is failing a lot
> is host-cargo.
>
> It fails like this:
>
>   = note: /usr/bin/ld: cannot find -lhttp_parser
>           collect2: error: ld returned 1 exit status
>
> error: aborting due to previous error
> error: Could not compile `cargo`.
>
> The problem is that while libhttp_parser gets built properly, cargo is
> not passing the appropriate -L flag to cargo's per-package host/lib
> directory. So the linker doesn't find the libhttp_parser library, and
> bails out.
>
> I've tried to look into this, but really the cargo build system is very
> unique and weird, and I'm having a hard time finding my way. Do you
> think you could help me a bit on this topic ?

Of course!

>
> To reproduce, you need a machine where libhttp_parser is not installed
> system-wide (so either remove it from your system, or build in a
> chroot/docker/VM). Then, take this branch:
>
>   https://git.bootlin.com/users/thomas-petazzoni/buildroot/log/?h=ppsh-v7-work
>
> And build the following defconfig:
>
> BR2_arm=y
> BR2_cortex_a9=y
> BR2_ARM_ENABLE_VFP=y
> BR2_PER_PACKAGE_DIRECTORIES=y
> BR2_TOOLCHAIN_EXTERNAL=y
> BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
> BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
> BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-arm-cortex-a9-glibc-2018.05.tar.bz2"
> BR2_TOOLCHAIN_EXTERNAL_GCC_7=y
> BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_16=y
> BR2_TOOLCHAIN_EXTERNAL_CUSTOM_GLIBC=y
> BR2_TOOLCHAIN_EXTERNAL_CXX=y
> BR2_INIT_NONE=y
> BR2_SYSTEM_BIN_SH_NONE=y
> # BR2_PACKAGE_BUSYBOX is not set
> # BR2_TARGET_ROOTFS_TAR is not set
> BR2_PACKAGE_HOST_CARGO=y
>
> You should get this failure:
>
>   http://code.bulix.org/fxjgrv-520980?raw
>
> Thanks in advance for your support,

I added your clone as remote, checked out ppsh-v7-work branch and
launched a Debian Stretch chroot. I'll keep you posted on the result.

Regards,

--
ELB

[Buildroot] Building cargo with per-package directories

[Eric Le Bihan]

On 2018-12-11 22:27, Eric Le Bihan wrote:
> Hi!
> On 2018-12-11 17:12, Thomas Petazzoni wrote:
> > Hello ?ric,
> >
> > As you probably know, I'm working on support for per-package
> > directories, which will allow to do top-level parallel in a reliable
> > way. As part of this effort, I've started an autobuilder that uses
> > per-package directories, and one of the package that is failing a lot
> > is host-cargo.
> >
> > It fails like this:
> >
> >   = note: /usr/bin/ld: cannot find -lhttp_parser
> >           collect2: error: ld returned 1 exit status
> >
> > error: aborting due to previous error
> > error: Could not compile `cargo`.
> >
> > The problem is that while libhttp_parser gets built properly, cargo is
> > not passing the appropriate -L flag to cargo's per-package host/lib
> > directory. So the linker doesn't find the libhttp_parser library, and
> > bails out.
> >
> > I've tried to look into this, but really the cargo build system is very
> > unique and weird, and I'm having a hard time finding my way. Do you
> > think you could help me a bit on this topic ?
>
> Of course!
>
> >
> > To reproduce, you need a machine where libhttp_parser is not installed
> > system-wide (so either remove it from your system, or build in a
> > chroot/docker/VM). Then, take this branch:
> >
> >   https://git.bootlin.com/users/thomas-petazzoni/buildroot/log/?h=ppsh-v7-work
> >
> > And build the following defconfig:
> >
> > BR2_arm=y
> > BR2_cortex_a9=y
> > BR2_ARM_ENABLE_VFP=y
> > BR2_PER_PACKAGE_DIRECTORIES=y
> > BR2_TOOLCHAIN_EXTERNAL=y
> > BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
> > BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
> > BR2_TOOLCHAIN_EXTERNAL_URL="http://autobuild.buildroot.org/toolchains/tarballs/br-arm-cortex-a9-glibc-2018.05.tar.bz2"
> > BR2_TOOLCHAIN_EXTERNAL_GCC_7=y
> > BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_16=y
> > BR2_TOOLCHAIN_EXTERNAL_CUSTOM_GLIBC=y
> > BR2_TOOLCHAIN_EXTERNAL_CXX=y
> > BR2_INIT_NONE=y
> > BR2_SYSTEM_BIN_SH_NONE=y
> > # BR2_PACKAGE_BUSYBOX is not set
> > # BR2_TARGET_ROOTFS_TAR is not set
> > BR2_PACKAGE_HOST_CARGO=y
> >
> > You should get this failure:
> >
> >   http://code.bulix.org/fxjgrv-520980?raw
> >
> > Thanks in advance for your support,
>
> I added your clone as remote, checked out ppsh-v7-work branch and
> launched a Debian Stretch chroot. I'll keep you posted on the result.

The build ended as expected.

```
  = note: /usr/bin/ld: cannot find -lhttp_parser
          collect2: error: ld returned 1 exit status
```

The library libhttp_parser.so is required by one of the dependencies of
cargo: libgit2-sys, which provides the Rust interface to libgit2.

There is trick in vendor/libgit2-sys/build.rs to handle
libhttp_parser.so: if the pkgconfig file of libgit2 contains -lhttp_parser,
then pass it to rustc via "cargo:rustc-link-lib=http_parser".

See "Outputs of the Build Script" in Cargo Book [1] for details.

We want to use per-package/host-cargo/host/lib/libhttp_parser.so. Adding
"-Clink-arg=-L$(HOST_DIR)/lib" to the RUSTFLAGS environment variable
solves the issue on my system:

```
diff --git a/package/cargo/cargo.mk b/package/cargo/cargo.mk
index 1b1053ba41..891901578e 100644
--- a/package/cargo/cargo.mk
+++ b/package/cargo/cargo.mk
@@ -70,7 +70,7 @@ HOST_CARGO_SNAP_OPTS = \
 	$(if $(VERBOSE),--verbose)

 HOST_CARGO_ENV = \
-	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib" \
+	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib -Clink-arg=-L$(HOST_DIR)/lib" \
 	CARGO_HOME=$(HOST_CARGO_HOME)

 define HOST_CARGO_BUILD_CMDS
```

[1] https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script

Regards,

--
ELB

[Buildroot] Building cargo with per-package directories

[Thomas Petazzoni]

Hello Eric,

On Wed, 12 Dec 2018 23:50:41 +0100, Eric Le Bihan wrote:

> The build ended as expected.
> 
> ```
>   = note: /usr/bin/ld: cannot find -lhttp_parser
>           collect2: error: ld returned 1 exit status
> ```
> 
> The library libhttp_parser.so is required by one of the dependencies of
> cargo: libgit2-sys, which provides the Rust interface to libgit2.
> 
> There is trick in vendor/libgit2-sys/build.rs to handle
> libhttp_parser.so: if the pkgconfig file of libgit2 contains -lhttp_parser,
> then pass it to rustc via "cargo:rustc-link-lib=http_parser".
> 
> See "Outputs of the Build Script" in Cargo Book [1] for details.
> 
> We want to use per-package/host-cargo/host/lib/libhttp_parser.so. Adding
> "-Clink-arg=-L$(HOST_DIR)/lib" to the RUSTFLAGS environment variable
> solves the issue on my system:
> 
> ```
> diff --git a/package/cargo/cargo.mk b/package/cargo/cargo.mk
> index 1b1053ba41..891901578e 100644
> --- a/package/cargo/cargo.mk
> +++ b/package/cargo/cargo.mk
> @@ -70,7 +70,7 @@ HOST_CARGO_SNAP_OPTS = \
>  	$(if $(VERBOSE),--verbose)
> 
>  HOST_CARGO_ENV = \
> -	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib" \
> +	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib -Clink-arg=-L$(HOST_DIR)/lib" \
>  	CARGO_HOME=$(HOST_CARGO_HOME)

Thanks a lot for this investigation and solution. I will definitely
have a look and see how it goes. Many, many thanks!

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[Buildroot] Building cargo with per-package directories

[Thomas Petazzoni]

Hello Eric,

On Wed, 12 Dec 2018 23:50:41 +0100, Eric Le Bihan wrote:

> diff --git a/package/cargo/cargo.mk b/package/cargo/cargo.mk
> index 1b1053ba41..891901578e 100644
> --- a/package/cargo/cargo.mk
> +++ b/package/cargo/cargo.mk
> @@ -70,7 +70,7 @@ HOST_CARGO_SNAP_OPTS = \
>  	$(if $(VERBOSE),--verbose)
> 
>  HOST_CARGO_ENV = \
> -	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib" \
> +	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib -Clink-arg=-L$(HOST_DIR)/lib" \
>  	CARGO_HOME=$(HOST_CARGO_HOME)
> 
>  define HOST_CARGO_BUILD_CMDS
> ```
> 
> [1] https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script

Thanks a lot, I was finally able to test this, and confirm it works
fine.

I propose to change it to:

	RUSTFLAGS="$(addprefix -Clink-arg=,$(HOST_LDFLAGS))"

so that if we ever change HOST_LDFLAGS in the future, it will continue
to work. What do you think ?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[Buildroot] Building cargo with per-package directories

[Eric Le Bihan]

On 2018-12-26 15:49, Thomas Petazzoni wrote:
> Hello Eric,
>
> On Wed, 12 Dec 2018 23:50:41 +0100, Eric Le Bihan wrote:
>
> > diff --git a/package/cargo/cargo.mk b/package/cargo/cargo.mk
> > index 1b1053ba41..891901578e 100644
> > --- a/package/cargo/cargo.mk
> > +++ b/package/cargo/cargo.mk
> > @@ -70,7 +70,7 @@ HOST_CARGO_SNAP_OPTS = \
> >  	$(if $(VERBOSE),--verbose)
> >
> >  HOST_CARGO_ENV = \
> > -	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib" \
> > +	RUSTFLAGS="-Clink-arg=-Wl,-rpath,$(HOST_DIR)/lib -Clink-arg=-L$(HOST_DIR)/lib" \
> >  	CARGO_HOME=$(HOST_CARGO_HOME)
> >
> >  define HOST_CARGO_BUILD_CMDS
> > ```
> >
> > [1] https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script
>
> Thanks a lot, I was finally able to test this, and confirm it works
> fine.
>
> I propose to change it to:
>
> 	RUSTFLAGS="$(addprefix -Clink-arg=,$(HOST_LDFLAGS))"
>
> so that if we ever change HOST_LDFLAGS in the future, it will continue
> to work. What do you think ?

I tested this change without issues, so I will post a patch to include
it in the cargo package.

Regards,

--
ELB

[Buildroot] Building cargo with per-package directories

[Thomas Petazzoni]

Hello Eric,

On Thu, 27 Dec 2018 21:50:15 +0100, Eric Le Bihan wrote:

> > so that if we ever change HOST_LDFLAGS in the future, it will continue
> > to work. What do you think ?  
> 
> I tested this change without issues, so I will post a patch to include
> it in the cargo package.

Thanks. In fact I already had a patch at
https://git.bootlin.com/users/thomas-petazzoni/buildroot/commit/?h=ppsh-v7-work&id=55c8e671d5130b22c72cedd194659c3dde5a6923,
but I will happily take an alternate patch if you have one.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[Buildroot] Building cargo with per-package directories

[Eric Le Bihan]

On 2018-12-28 10:21, Thomas Petazzoni wrote:
> Hello Eric,
>
> On Thu, 27 Dec 2018 21:50:15 +0100, Eric Le Bihan wrote:
>
> > > so that if we ever change HOST_LDFLAGS in the future, it will continue
> > > to work. What do you think ?
> >
> > I tested this change without issues, so I will post a patch to include
> > it in the cargo package.
>
> Thanks. In fact I already had a patch at
> https://git.bootlin.com/users/thomas-petazzoni/buildroot/commit/?h=ppsh-v7-work&id=55c8e671d5130b22c72cedd194659c3dde5a6923,
> but I will happily take an alternate patch if you have one.

I do not have one yet, so your patch is fine.

Regards,

--
ELB