support custom specs for compilers

docs/recipes.md

@@ -120,7 +120,31 @@ The first step - building `gcc` - is required, so that the simplest stack will p
 
     * `nvhpc:version:"21.7"` generates `nvhpc@21.7 ~mpi~blas~lapack`
     * `llvm:version:"14"` generates `llvm@14 +clang ~gold`
-    * `gcc:version:"13"` generates `gcc@13 build_type=Release +profiled +strip +bootstrap`
+    * `gcc:version:"13"` generates `gcc@13 +bootstrap`
+
+The default variants can be customised by setting the optional `spec` field on a compiler, which **replaces** the default variants for that compiler:
+
+```yaml title="compilers.yaml with a custom gcc spec"
+gcc:
+  version: "13"
+  spec: "~bootstrap+nvptx"   # generates gcc@13 ~bootstrap+nvptx
+llvm:
+  version: "16"              # generates the default llvm@16 +clang ~gold
+```
+
+The `spec` string is appended verbatim to `name@version`.
+Because it replaces the defaults, restate any default variants that should be kept.
+
+!!! example "`gcc` with support for openmp offload on GPU"
+    ```yaml title='cuda offload'
+    gcc:
+        version: "15" # compatible with cuda@13.x
+        speac: "+nvptx~bootstrap"
+    ```
+    Bootstrapping needs to be explicitly disabled to compile gcc.
+
+!!! note
+    The `spec` field is ignored when `gcc:version` is `system`.
 
 ## Environments
 

stackinator/recipe.py

@@ -497,19 +497,26 @@ def generate_compiler_specs(self, raw):
 
         gcc_version = raw["gcc"]["version"]
         if gcc_version == "system":
+            if raw["gcc"].get("spec"):
+                self._logger.warning("compilers.yaml: the 'spec' field is ignored when gcc version is 'system'")
             compilers["gcc"] = {"system": True}
         else:
-            compilers["gcc"] = {"specs": [f"gcc@{gcc_version} +bootstrap"], "version": gcc_version}
-
-        for name, spec_template in [
-            ("nvhpc", "nvhpc@{version} ~mpi~blas~lapack"),
-            ("llvm", "llvm@{version} +clang ~gold"),
-            ("llvm-amdgpu", "llvm-amdgpu@{version}"),
-            ("intel-oneapi-compilers", "intel-oneapi-compilers@{version}"),
+            suffix = raw["gcc"].get("spec") or "+bootstrap"
+            compilers["gcc"] = {"specs": [f"gcc@{gcc_version} {suffix}"], "version": gcc_version}
+
+        # the default spec (variants etc) for each compiler, used when the recipe
+        # does not provide an explicit 'spec' field
+        for name, default_suffix in [
+            ("nvhpc", "~mpi~blas~lapack"),
+            ("llvm", "+clang ~gold"),
+            ("llvm-amdgpu", ""),
+            ("intel-oneapi-compilers", ""),
         ]:
             if raw.get(name) is not None:
                 version = raw[name]["version"]
-                compilers[name] = {"specs": [spec_template.format(version=version)], "version": version}
+                suffix = raw[name].get("spec") or default_suffix
+                spec = f"{name}@{version} {suffix}".strip()
+                compilers[name] = {"specs": [spec], "version": version}
 
         self.compilers = compilers
 

stackinator/schema/compilers.json

@@ -8,7 +8,14 @@
         "gcc": {
             "type": "object",
             "properties": {
-                "version": {"type": "string"}
+                "version": {"type": "string"},
+                "spec": {
+                    "oneOf": [
+                        {"type": "string"},
+                        {"type": "null"}
+                    ],
+                    "default": null
+                }
             },
             "additionalProperties": false,
             "required": ["version"]
@@ -18,7 +25,14 @@
                 {
                     "type": "object",
                     "properties": {
-                        "version": {"type": "string"}
+                        "version": {"type": "string"},
+                        "spec": {
+                            "oneOf": [
+                                {"type": "string"},
+                                {"type": "null"}
+                            ],
+                            "default": null
+                        }
                     },
                     "additionalProperties": false,
                     "required": ["version"]
@@ -34,7 +48,14 @@
                 {
                     "type": "object",
                     "properties": {
-                        "version": {"type": "string"}
+                        "version": {"type": "string"},
+                        "spec": {
+                            "oneOf": [
+                                {"type": "string"},
+                                {"type": "null"}
+                            ],
+                            "default": null
+                        }
                     },
                     "additionalProperties": false,
                     "required": ["version"]
@@ -50,7 +71,14 @@
                 {
                     "type": "object",
                     "properties": {
-                        "version": {"type": "string"}
+                        "version": {"type": "string"},
+                        "spec": {
+                            "oneOf": [
+                                {"type": "string"},
+                                {"type": "null"}
+                            ],
+                            "default": null
+                        }
                     },
                     "additionalProperties": false,
                     "required": ["version"]
@@ -66,7 +94,14 @@
                 {
                     "type": "object",
                     "properties": {
-                        "version": {"type": "string"}
+                        "version": {"type": "string"},
+                        "spec": {
+                            "oneOf": [
+                                {"type": "string"},
+                                {"type": "null"}
+                            ],
+                            "default": null
+                        }
                     },
                     "additionalProperties": false,
                     "required": ["version"]

unittests/test_recipe.py

@@ -1,13 +1,16 @@
+import logging
+
 import pytest
 
 from stackinator.recipe import Recipe
 from stackinator.spack_util import Version
 
 
-def make_recipe(commit):
+def make_recipe(commit=None):
     """A Recipe with only the spack config populated, bypassing the heavy __init__."""
     recipe = Recipe.__new__(Recipe)
     recipe._config = {"spack": {"commit": commit}}
+    recipe._logger = logging.getLogger("test_recipe")
     return recipe
 
 
@@ -39,3 +42,47 @@ def test_find_spack_version_develop_flag():
     """The --develop flag targets the develop branch of spack, now at 1.2."""
     recipe = make_recipe("releases/v1.0")
     assert recipe.find_spack_version(develop=True) == Version(1, 2)
+
+
+def test_generate_compiler_specs_defaults():
+    """Without a 'spec' field, each compiler gets its default variants."""
+    recipe = make_recipe()
+    recipe.generate_compiler_specs(
+        {
+            "gcc": {"version": "13", "spec": None},
+            "nvhpc": {"version": "25.1", "spec": None},
+            "llvm": {"version": "16", "spec": None},
+            "llvm-amdgpu": {"version": "6.0", "spec": None},
+            "intel-oneapi-compilers": {"version": "2024.1", "spec": None},
+        }
+    )
+    assert recipe.compilers["gcc"]["specs"] == ["gcc@13 +bootstrap"]
+    assert recipe.compilers["nvhpc"]["specs"] == ["nvhpc@25.1 ~mpi~blas~lapack"]
+    assert recipe.compilers["llvm"]["specs"] == ["llvm@16 +clang ~gold"]
+    assert recipe.compilers["llvm-amdgpu"]["specs"] == ["llvm-amdgpu@6.0"]
+    assert recipe.compilers["intel-oneapi-compilers"]["specs"] == ["intel-oneapi-compilers@2024.1"]
+    assert not recipe.use_system_gcc
+
+
+def test_generate_compiler_specs_custom_spec():
+    """A 'spec' field replaces the default variants for that compiler."""
+    recipe = make_recipe()
+    recipe.generate_compiler_specs(
+        {
+            "gcc": {"version": "13", "spec": "~bootstrap+nvptx"},
+            "nvhpc": {"version": "25.1", "spec": None},
+            "llvm": {"version": "16", "spec": "+clang +flang ~gold"},
+        }
+    )
+    assert recipe.compilers["gcc"]["specs"] == ["gcc@13 ~bootstrap+nvptx"]
+    # nvhpc keeps the default variants
+    assert recipe.compilers["nvhpc"]["specs"] == ["nvhpc@25.1 ~mpi~blas~lapack"]
+    assert recipe.compilers["llvm"]["specs"] == ["llvm@16 +clang +flang ~gold"]
+
+
+def test_generate_compiler_specs_system_gcc():
+    """A custom spec is ignored when the system gcc is used."""
+    recipe = make_recipe()
+    recipe.generate_compiler_specs({"gcc": {"version": "system", "spec": "+nvptx"}})
+    assert recipe.compilers["gcc"] == {"system": True}
+    assert recipe.use_system_gcc

unittests/test_schema.py

@@ -117,15 +117,19 @@ def test_compilers_yaml(yaml_path):
     with open(yaml_path / "compilers.defaults.yaml") as fid:
         raw = yaml.load(fid, Loader=yaml.Loader)
         schema.CompilersValidator.validate(raw)
-        assert raw["gcc"] == {"version": "10.2"}
+        assert raw["gcc"] == {"version": "10.2", "spec": None}
         assert raw["llvm"] is None
 
     with open(yaml_path / "compilers.full.yaml") as fid:
         raw = yaml.load(fid, Loader=yaml.Loader)
         schema.CompilersValidator.validate(raw)
-        assert raw["gcc"] == {"version": "11"}
-        assert raw["llvm"] == {"version": "13"}
-        assert raw["nvhpc"] == {"version": "25.1"}
+        assert raw["gcc"] == {"version": "11", "spec": "~bootstrap+nvptx"}
+        assert raw["llvm"] == {"version": "13", "spec": None}
+        assert raw["nvhpc"] == {"version": "25.1", "spec": None}
+
+    # spec must be a string (or null)
+    with pytest.raises(schema.ValidationError):
+        schema.CompilersValidator.validate({"gcc": {"version": "13", "spec": ["+nvptx"]}})
 
 
 def test_recipe_compilers_yaml(recipe_paths):

unittests/yaml/compilers.full.yaml

@@ -1,5 +1,6 @@
 gcc:
   version: "11"
+  spec: "~bootstrap+nvptx"
 llvm:
   version: "13"
 nvhpc: