# How to specify Ada runtime with GPRbuild

**URL:** https://forum.ada-lang.io/t/how-to-specify-ada-runtime-with-gprbuild/4481
**Category:** Help
**Created:** [June 6, 2026, 11:04am UTC](https://forum.ada-lang.io/t/how-to-specify-ada-runtime-with-gprbuild/4481 "2026-06-06T11:04:54Z")
**Posts on this page:** 1
**Showing post:** 10

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### Author: ![SadClouds](https://forum.ada-lang.io/letter_avatar_proxy/v4/letter/s/22d042/32.png) [@SadClouds](https://forum.ada-lang.io/u/SadClouds)
#### Post date: [June 7, 2026, 7:51am UTC](https://forum.ada-lang.io/t/how-to-specify-ada-runtime-with-gprbuild/4481/10 "2026-06-07T07:51:10Z")

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I tried to debug it before, see this thread: [https://forum.ada-lang.io/t/gprconfig-for-bare-metal-target/4409](https://forum.ada-lang.io/t/gprconfig-for-bare-metal-target/4409)

I’m not sure how GNAT Pro build their cross-compilers, but I’m building a bare metal sparc64 cross-compiler without any Ada runtime, which is also missing a few other tools like `gnatls`. I think `gprconfig` may be missing some logic to correctly identify such cross-compilers. It finds sparc64 C and Asm compilers, but refuses to find Ada compiler. There is no indication why. The Ada compiler is definitely there, because I can use it to build sparc64 object files, i.e. when building Ada runtime. This is the reason I had to create a custom \*.cgpr file to workaround these issues.

I’m not sure if this is a bug with `gprconfig` or if there is a different strategy for building Ada cross-compilers. Following your suggestion, below is the command invoked by `gprbuild`:

```ada
PATH="${HOME:?}/gcc-15.2.0_native/bin:${HOME:?}/gcc-15.2.0_sparc64-unknown-elf/bin" \
  /home/user/gcc-15.2.0_native/bin/gprconfig -vv --batch \
  -o /tmp/out --target=sparc64-unknown-elf \
  --config=c,,,, --config=ada,,/home/user/bare_runtime,,
...
gprconfig: can't find a toolchain for the following configuration:
gprconfig: language 'ada', target 'sparc64-unknown-elf', runtime '/home/user/bare_runtime'

```

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