Inspired by me setting a breakpoint on a function and gdb telling me there are 12 locations...
The idea behind the *-inl.h files is to provide inline definitions of short functions. Large gobs of code don't belong in them because they negatively impact:
- Compile times
- Binary size (duplication)
- Run-time performance (instruction cache pressure)
Rules of thumb:
- Functions with few or infrequent callers should (judgment call) live in a
.cc file
- Functions over 4-5 lines that aren't template functions should live in a
.cc file
- Macros like
CHECK(..) expand to multiple lines of code and should be counted as such
Good (short, many callers):
|
inline v8::Isolate* IsolateData::isolate() const { |
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return isolate_; |
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} |
Not good (big, only two infrequent callers):
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inline void Environment::AssignToContext(v8::Local<v8::Context> context, |
|
const ContextInfo& info) { |
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context->SetAlignedPointerInEmbedderData( |
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ContextEmbedderIndex::kEnvironment, this); |
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// Used by Environment::GetCurrent to know that we are on a node context. |
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context->SetAlignedPointerInEmbedderData( |
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ContextEmbedderIndex::kContextTag, Environment::kNodeContextTagPtr); |
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// Used to retrieve bindings |
|
context->SetAlignedPointerInEmbedderData( |
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ContextEmbedderIndex::kBindingListIndex, &(this->bindings_)); |
|
|
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#if HAVE_INSPECTOR |
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inspector_agent()->ContextCreated(context, info); |
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#endif // HAVE_INSPECTOR |
|
|
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this->async_hooks()->AddContext(context); |
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} |
Questionable (single infrequent caller):
|
inline void Environment::TryLoadAddon( |
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const char* filename, |
|
int flags, |
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const std::function<bool(binding::DLib*)>& was_loaded) { |
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loaded_addons_.emplace_back(filename, flags); |
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if (!was_loaded(&loaded_addons_.back())) { |
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loaded_addons_.pop_back(); |
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} |
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} |
The most commonly used *-inl.h files are:
$ find src -type f | xargs perl -ne 'print "$1\n" if /#\s*include "([^"]+-inl.h)"/' | sort | uniq -c | sort -r | head -9
91 env-inl.h
74 util-inl.h
52 memory_tracker-inl.h
42 base_object-inl.h
35 async_wrap-inl.h
29 debug_utils-inl.h
19 threadpoolwork-inl.h
18 node_process-inl.h
15 stream_base-inl.h
Inspired by me setting a breakpoint on a function and gdb telling me there are 12 locations...
The idea behind the
*-inl.hfiles is to provide inline definitions of short functions. Large gobs of code don't belong in them because they negatively impact:Rules of thumb:
.ccfile.ccfileCHECK(..)expand to multiple lines of code and should be counted as suchGood (short, many callers):
node/src/env-inl.h
Lines 56 to 58 in 7d13f5e
Not good (big, only two infrequent callers):
node/src/env-inl.h
Lines 349 to 365 in 7d13f5e
Questionable (single infrequent caller):
node/src/env-inl.h
Lines 510 to 518 in 7d13f5e
The most commonly used
*-inl.hfiles are: