// Copyright 2017 The Bazel Authors. All rights reserved. // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package com.google.devtools.build.lib.analysis; import static com.google.common.truth.Truth.assertThat; import com.google.devtools.build.lib.analysis.util.BuildViewTestBase; import com.google.devtools.build.lib.skyframe.BuildConfigurationValue; import com.google.devtools.build.lib.skyframe.SkyframeBuildView; import org.junit.Test; import org.junit.runner.RunWith; import org.junit.runners.JUnit4; /** * Tests for {@link OutputFileConfiguredTarget}. */ @RunWith(JUnit4.class) public class OutputFileConfiguredTargetTest extends BuildViewTestBase { @Test public void generatingRuleIsCorrect() throws Exception { scratch.file("foo/BUILD", "genrule(", " name='generating_rule', ", " cmd = 'echo hi > $@',", " srcs = [],", " outs = ['generated.source'])"); update("//foo:generating_rule"); OutputFileConfiguredTarget generatedSource = (OutputFileConfiguredTarget) getConfiguredTarget("//foo:generated.source", getHostConfiguration()); assertThat(generatedSource.getGeneratingRule()) .isSameAs(getConfiguredTarget("//foo:generating_rule", getHostConfiguration())); } /** * This regression-tests the fix for a bug in which Bazel could crash with a NullPointerException * when two builds were invoked with different configurations because an output file ended up * unexpectedly having a null generating rule. * *
The reasons for this are subtle and complex. In short, the bug only happens when * --experimental_dynamic_configs=off and BuildConfiguration.equals provides value equality. * *
In that scenario, when we call {@code bazel build //foo:gen1 --copt a=b}, Bazel creates a * host configuration H1 for this build that attaches to {@code * //foo:host_generated_file_producer} (which is the generator of {@code host_src1.cc}). * *
When we then call {@code bazel build //foo:gen2 --copt a=c}, the options have changed so * Bazel clears all configurations and configured targets. This includes the host configuration, * even though - importantly - none of its options have changed. So Bazel uses a new host config * H2 that's value-equal to H1 (but not reference-equal) and assigns it to {@code host_src2.cc}. * *
Here's the problem: during configured target analysis, Bazel creates the configured target
* When configs only use reference equality, the problem goes away because the interner can no
* longer safely merge H1 and H2. An alternative fix might be to change
* {@link TargetContext#findDirectPrerequisite} to check {@code config.equals(H2)} instead of
* {@code config == H2}. But this isn't really safe because static configs embed references to
* other configs in their transition table. So returning H1 when you expect H2 creates the
* possibility of "leaking out" to the wrong configuration during a transition, even if H1 and H2
* have the same exact build options.
*
* All of these problems go away with dynamic configurations. This is for two reasons: 1)
* dynamic configs don't embed transition tables, so "leaking out" is no longer possible. And
* 2) a dynamic config is evaluated through Skyframe keyed on its BuildOptions, so semantic
* equality implies reference equality anyway, 2 may change in the future, but if/when it does
* this test should reliably fail so appropriate measures can be taken.
*/
@Test
public void regressionTestForStaticConfigsWithValueEquality() throws Exception {
scratch.file("foo/BUILD",
"genrule(",
" name = 'host_generated_file_producer',",
" srcs = [],",
" outs = [",
" 'host_src1.cc',",
" 'host_src2.cc',",
" ],",
" cmd = 'echo hi > $(location host_src1.cc); echo hi > $(location host_src2.cc)')",
"",
"cc_binary(",
" name = 'host_generated_file_consumer1',",
" srcs = ['host_src1.cc'])",
"",
"cc_binary(",
" name = 'host_generated_file_consumer2',",
" srcs = ['host_src2.cc'])",
"",
"genrule(",
" name = 'gen1',",
" srcs = [],",
" outs = ['gen1.out'],",
" cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer1'])",
"",
"genrule(",
" name = 'gen2',",
" srcs = [],",
" outs = ['gen2.out'],",
" cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer2'])"
);
useConfiguration("--copt", "a=b");
update("//foo:gen1");
useConfiguration("--copt", "a=c");
update("//foo:gen2");
OutputFileConfiguredTarget hostSrc2 = (OutputFileConfiguredTarget)
getConfiguredTarget("//foo:host_src2.cc", getHostConfiguration());
assertThat(hostSrc2.getGeneratingRule()).isNotNull();
}
/**
* Dynamic configurations maintain a host configuration cache that stores configurations
* instantiated outside of Skyframe. We shouldn't, in general, instantiate configurations
* outside of {@link BuildConfigurationValue}. But in this specific case Bazel performance
* suffers through the Skyframe interface and maintaining a local cache is much faster.
* See {@link SkyframeBuildView} for details.
*
* One consequence of this is that requesting a config that would be a Skyframe cache hit
* can still produce a distinct instance. Meaning you can get cases where {@code
* config1.equals(config2) && config1 != config2}.
*
* This test checks for such a case: perform three consecutive Bazel builds. The first builds
* with default options, producing top-level host config H1 and configured target
* This produces the expected scenario where the output file's config is value-equal but not
* reference-equal to its generating rule's config.
*/
@Test
public void dynamicConfigsWithHostConfigSwitch() throws Exception {
scratch.file("foo/BUILD",
"genrule(",
" name = 'host_generated_file_producer',",
" srcs = [],",
" outs = [",
" 'host_src1.cc',",
" 'host_src2.cc',",
" 'host_src3.cc',",
" ],",
" cmd = 'echo hi > $(location host_src1.cc); echo hi > $(location host_src2.cc); "
+ "echo hi > $(location host_src3.cc)')",
"",
"cc_binary(name = 'host_generated_file_consumer1', srcs = ['host_src1.cc'])",
"cc_binary(name = 'host_generated_file_consumer2', srcs = ['host_src2.cc'])",
"cc_binary(name = 'host_generated_file_consumer3', srcs = ['host_src3.cc'])",
"",
"genrule(name = 'gen1', srcs = [], outs = ['gen1.out'], cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer1'])",
"genrule(name = 'gen2', srcs = [], outs = ['gen2.out'], cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer2'])",
"genrule(name = 'gen3', srcs = [], outs = ['gen3.out'], cmd = 'echo hi > $@',",
" tools = [':host_generated_file_consumer3'])");
String dynamicConfigsMode = "--experimental_dynamic_configs=notrim";
useConfiguration(dynamicConfigsMode);
update("//foo:gen1");
useConfiguration(dynamicConfigsMode, "--host_copt", "a=b");
update("//foo:gen2");
useConfiguration(dynamicConfigsMode);
update("//foo:gen3");
OutputFileConfiguredTarget hostSrc3 = (OutputFileConfiguredTarget)
getConfiguredTarget("//foo:host_src3.cc", getHostConfiguration());
TransitiveInfoCollection hostGeneratedFileConsumer3 = hostSrc3.getGeneratingRule();
assertThat(hostSrc3.getConfiguration())
.isEqualTo(hostGeneratedFileConsumer3.getConfiguration());
// TODO(gregce): enable below for Bazel tests, which for some reason realize the same instance
// assertThat(hostSrc3.getConfiguration())
// .isNotSameAs(hostGeneratedFileConsumer3.getConfiguration());
}
}