undefined reference to 'rust_begin_unwind': {start,end}-group missing when using an allocator

[japaric]

STR

$ cargo clone cortex-m-quickstart --vers 0.3.2

$ cd cortex-m-quickstart

$ cat > memory.x <<EOF
/* Linker script for the STM32F103C8T6 */
MEMORY
{
  FLASH : ORIGIN = 0x08000000, LENGTH = 64K
  RAM : ORIGIN = 0x20000000, LENGTH = 20K
}
EOF

$ # OK, doesn't use an allocator
$ # NOTE depends on arm-none-eabi-gcc being installed
$ cargo build --example hello --target thumbv7m-none-eabi

$ cargo add alloc-cortex-m --vers 0.3.5

$ # fails to link
$ cargo build --example allocator --target thumbv7m-none-eabi
  = note: "arm-none-eabi-gcc" (..)
  = note: $_/libcore-c8a4409079a3a8cf.rlib(core-c8a4409079a3a8cf.core7-a6f8712c77d6e222f682a36ad1b2802c.rs.rcgu.o): In function `core::panicking::panic_fmt':
          /checkout/src/libcore/panicking.rs:92: undefined reference to `rust_begin_unwind'

AFAICT the issue is that the linker call in the allocator example doesn't include the -Wl,--{start,end}-group flags added in #49316. Linker invocation for each example is shown below:

Details

$ cargo rustc --example hello --target thumbv7m-none-eabi -- -Z print-link-args "arm-none-eabi-gcc" "-L" "/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/hello-7bcb38c76f2cfcf9.16u6js6g0l3k1ic6.rcgu.o" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/hello-7bcb38c76f2cfcf9.3l0398fjltevyo2h.rcgu.o" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/hello-7bcb38c76f2cfcf9.4xq48u46a1pwiqn7.rcgu.o" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/hello-7bcb38c76f2cfcf9.544l4wfz89vbhoea.rcgu.o" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/hello-7bcb38c76f2cfcf9.8xzrsc1ux72v29j.rcgu.o" "-o" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/hello-7bcb38c76f2cfcf9" "-Wl,--gc-sections" "-nodefaultlibs" "-L" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps" "-L" "/home/japaric/tmp/cortex-m-quickstart/target/debug/deps" "-L" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-quickstart-83c2769bb84a5327/out" "-L" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-91d6bcd8221521d0/out" "-L" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-rt-8f472c01bb62b44f/out" "-L" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-rt-8f472c01bb62b44f/out" "-L" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-semihosting-0b565ca91223cdc9/out" "-L" "/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib" "-Wl,--start-group" "-Wl,-Bstatic" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libpanic_semihosting-5bedc9c7e9038e5a.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libcortex_m-608790ed92cdaba8.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libvolatile_register-febb9ecda2e1e875.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libvcell-5f0330b175b9171f.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libbare_metal-cd38b616da4ad7a9.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libaligned-65d7a0374e7cc15f.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libcortex_m_semihosting-2b99179dc7319028.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libcortex_m_rt-df2a73939030a238.rlib" "/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libr0-0230fc14e4aa7a0c.rlib" "/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/libcore-c8a4409079a3a8cf.rlib" "-Wl,--end-group" "/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/libcompiler_builtins-a0b503090929f0e3.rlib" "-Wl,-Tlink.x" "-nostartfiles" "-Wl,-Bdynamic"

$ cargo build --example allocator --target thumbv7m-none-eabi
"arm-none-eabi-gcc"
"-L"
"/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.12o6z8zowpxdwec2.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.16u6js6g0l3k1ic6.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.181cuta0v63atwcm.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.1im38lueib99jsk0.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.1mvmz58owquyropc.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.1y16o1qfye96o7m0.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.2lyh15q6cjwzy18c.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.2njzq1xnlu88l3yx.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.2oafmlh5ijbov6fd.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.3ayaeypdcro9d6yk.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.3l0398fjltevyo2h.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.48721dc4k5qxei0u.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.49a7n47po4ttqjl7.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.4ezmh1vbs95c5ack.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.4kcm5l1y0r3i2da7.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.4xq48u46a1pwiqn7.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.4yh8x2b62dcih00t.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.51s1w397y42gpez1.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.56dly8q07ws8ucdq.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.8xzrsc1ux72v29j.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.9elsx31vb4it187.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.9fcb3syd3ne5k0n.rcgu.o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.y08g5q2x813c4wx.rcgu.o"
"-o"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/examples/allocator-d041c1c8fc06f1f7.crate.allocator.rcgu.o"
"-Wl,--gc-sections"
"-nodefaultlibs"
"-L"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps"
"-L"
"/home/japaric/tmp/cortex-m-quickstart/target/debug/deps"
"-L"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-quickstart-83c2769bb84a5327/out"
"-L"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-91d6bcd8221521d0/out"
"-L"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-rt-8f472c01bb62b44f/out"
"-L"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-rt-8f472c01bb62b44f/out"
"-L"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/build/cortex-m-semihosting-0b565ca91223cdc9/out"
"-L"
"/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib"
"-Wl,-Bstatic"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libpanic_semihosting-5bedc9c7e9038e5a.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libcortex_m_semihosting-2b99179dc7319028.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libcortex_m_rt-df2a73939030a238.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libr0-0230fc14e4aa7a0c.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libcortex_m-608790ed92cdaba8.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libvolatile_register-febb9ecda2e1e875.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libvcell-5f0330b175b9171f.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libbare_metal-cd38b616da4ad7a9.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libaligned-65d7a0374e7cc15f.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/liballoc_cortex_m-1dc8f624614f3e20.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/liblinked_list_allocator-89856fc389dfa7e0.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libcortex_m-d4954d2588102c99.rlib"
"/home/japaric/tmp/cortex-m-quickstart/target/thumbv7m-none-eabi/debug/deps/libvolatile_register-7f8b6601fedcc83f.rlib"
"/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/liballoc-0cbd0a7c85435046.rlib"
"/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/libcore-c8a4409079a3a8cf.rlib"
"/home/japaric/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/libcompiler_builtins-a0b503090929f0e3.rlib"
"-Wl,-Tlink.x"
"-nostartfiles"
"-Wl,-Bdynamic"

Adding -Wl,--{start,end}-group to the linker invocation for the allocator example fixes the linking error.

I believe this error started showing up after #50144 landed.

Meta

$ rustc -V
rustc 1.28.0-nightly (523097979 2018-06-18)

cc @alexcrichton @sfackler

[japaric]

This may be related to, or even directly caused by, #51671. If I move the oom lang item into a separate crate (rlib) then --{start,end}-group appear in the linker invocation and linking succeeds.

[japaric]

This may be related to, or even directly caused by, #51671.

#51671 has been fixed but this problem still remains: the {start,end}-group linker flags are still missing -- the rust_oom and rust_begin_unwind are present in the object files.

[japaric]

I can no longer reproduce this.