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- Separate inline headers: We allow putting inline functions in separate files, using the suffix
.inline.h
. This can speed up compile times by reducing the volume of code to be compiled and reducing dependencies between headers. - Header include guards: for new code, we prefer #pragma once because it is cleaner than the classic #include guards
Variable Naming
We use UPPER_CASE for constants instead of kConstantName.
Scoping
- namespaces the
using namespace
directive is allowed in .cc files in limited cases where it greatly reduces code volume.- Pros: reduces code volume, less churn in "using namespace::class" directives.
- Cons: pollutes the namespace, causes conflicts, makes it more difficult to determine the type of an object
Commenting
- TODO Comments we typically do not include the name in the TODO comment. Where possible it's best to fix the TODO immediately (if it is a small task) or create a JIRA to track a more substantial improvement.
Formatting
The .clang-format file checked into the Impala repository should be used to format whitespace (see Contributing to Impala for more info). The .clang-format file is the source of truth for whitespace formatting, except when its output significantly diverges from practices in the existing codebase or from common sense. In those cases .clang-format should be updated. We aim to gradually adapt the codebase to the output of clang-format Therefore we only recommend using it on lines that have non-whitespace changes. This can be accomplished with the git-clang-format tool.
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// Google Recommends: ReturnType LongClassName::ReallyReallyReallyLongFunctionName( Type par_name1, // 4 space indent Type par_name2, Type par_name3) { DoSomething(); // 2 space indent ... } // we use: ReturnType LongClassName::ReallyReallyReallyLongFunctionName( Type par_name1, Type par_name2, Type par_name3) { // 4 space indent DoSomething(); // 2 space indent ... } |
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3. Conditionals we format conditionals as follows
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git diff -U0 --no-color HEAD^ | "${IMPALA_TOOLCHAIN_PACKAGES_HOME}/llvm-${IMPALA_LLVM_VERSION}/share/clang/clang-format-diff.py" -binary "${IMPALA_TOOLCHAIN_PACKAGES_HOME}/llvm-${IMPALA_LLVM_VERSION}/bin/clang-format" -p1 -i |
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sudo apt-get install clang-format-3.9 git diff -U0 --no-color HEAD^ | clang-format-diff-3.9 -p1 -i |
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Info | ||
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clang-format is not perfect and sometimes reformats things in strange ways, or will reformat large areas of code. If clang-format doesn't match the existing style of the surrounding code, please consider manually formatting that part of the code - mixing large white |
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git diff asf-gerrit/master | "${IMPALA_TOOLCHAIN_PACKAGES_HOME}/llvm-${IMPALA_LLVM_VERSION}/share/clang/clang-tidy-diff.py" -clang-tidy-binary "${IMPALA_TOOLCHAIN_PACKAGES_HOME}/llvm-${IMPALA_LLVM_VERSION}/bin/clang-tidy" -p 1 |
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