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[docs] Coverage: Flesh out instructions for avoiding static initializeres 

llvm-svn: 272214
This commit is contained in:
Vedant Kumar 2016-06-08 22:24:52 +00:00
parent 98102e7447
commit 32a9bfa42a
1 changed files with 14 additions and 6 deletions
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20
clang/docs/SourceBasedCodeCoverage.rst
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@ -192,14 +192,22 @@ By default the compiler runtime uses a static initializer to determine the
profile output path and to register a writer function. To collect profiles profile output path and to register a writer function. To collect profiles
without using static initializers, do this manually: without using static initializers, do this manually:
* Export a ``int __llvm_profile_runtime`` symbol. The linker won't pull in the * Export a ``int __llvm_profile_runtime`` symbol from each instrumented shared
object file containing the profiling runtime's static initializer if this library and executable. When the linker finds a definition of this symbol, it
symbol is defined. knows to skip loading the object which contains the profiling runtime's
static initializer.
* Call ``__llvm_profile_initialize_file`` once. This parses * Forward-declare ``void __llvm_profile_initialize_file(void)`` and call it
``LLVM_PROFILE_FILE`` and sets the output path. once from each instrumented executable. This function parses
``LLVM_PROFILE_FILE``, sets the output path, and truncates any existing files
at that path. To get the same behavior without truncating existing files,
pass a filename pattern string to ``void __llvm_profile_set_filename(char
*)``. These calls can be placed anywhere so long as they precede all calls
to ``__llvm_profile_write_file``.
* Call ``__llvm_profile_write_file`` to write out a profile. * Forward-declare ``int __llvm_profile_write_file(void)`` and call it to write
out a profile. Calling this function multiple times appends profile data to
an existing on-disk raw profile.
Drawbacks and limitations Drawbacks and limitations
========================= =========================