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Diffstat (limited to 'docs/PTHInternals.html')
| -rw-r--r-- | docs/PTHInternals.html | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/docs/PTHInternals.html b/docs/PTHInternals.html index 832d3b0..279d479 100644 --- a/docs/PTHInternals.html +++ b/docs/PTHInternals.html @@ -23,38 +23,38 @@ implementation. If you are interested in the end-user view, please see the <a href="UsersManual.html#precompiledheaders">User's Manual</a>.</p> -<h2>Using Pretokenized Headers with <tt>clang-cc</tt> (Low-level Interface)</h2> +<h2>Using Pretokenized Headers with <tt>clang</tt> (Low-level Interface)</h2> -<p>The low-level Clang compiler tool, <tt>clang-cc</tt>, supports three command -line options for generating and using PTH files.<p> +<p>The Clang compiler frontend, <tt>clang -cc1</tt>, supports three command line +options for generating and using PTH files.<p> -<p>To generate PTH files using <tt>clang-cc</tt>, use the option +<p>To generate PTH files using <tt>clang -cc1</tt>, use the option <b><tt>-emit-pth</tt></b>: -<pre> $ clang-cc test.h -emit-pth -o test.h.pth </pre> +<pre> $ clang -cc1 test.h -emit-pth -o test.h.pth </pre> <p>This option is transparently used by <tt>clang</tt> when generating PTH files. Similarly, PTH files can be used as prefix headers using the <b><tt>-include-pth</tt></b> option:</p> <pre> - $ clang-cc -include-pth test.h.pth test.c -o test.s + $ clang -cc1 -include-pth test.h.pth test.c -o test.s </pre> <p>Alternatively, Clang's PTH files can be used as a raw "token-cache" (or "content" cache) of the source included by the original header file. This means that the contents of the PTH file are searched as substitutes -for <em>any</em> source files that are used by <tt>clang-cc</tt> to process a +for <em>any</em> source files that are used by <tt>clang -cc1</tt> to process a source file. This is done by specifying the <b><tt>-token-cache</tt></b> option:</p> <pre> $ cat test.h #include <stdio.h> - $ clang-cc -emit-pth test.h -o test.h.pth + $ clang -cc1 -emit-pth test.h -o test.h.pth $ cat test.c #include "test.h" - $ clang-cc test.c -o test -token-cache test.h.pth + $ clang -cc1 test.c -o test -token-cache test.h.pth </pre> <p>In this example the contents of <tt>stdio.h</tt> (and the files it includes) @@ -117,7 +117,7 @@ PTH file needs to be generated during a build instead of several.</p></li> <li><p><b>Reduced memory pressure</b>: Similar to GCC, Clang reads PTH files via the use of memory mapping (i.e., <tt>mmap</tt>). Clang, however, memory maps PTH files as read-only, meaning that multiple -invocations of <tt>clang-cc</tt> can share the same pages in memory from a +invocations of <tt>clang -cc1</tt> can share the same pages in memory from a memory-mapped PTH file. In comparison, GCC also memory maps its PCH files but also modifies those pages in memory, incurring the copy-on-write costs. The read-only nature of PTH can greatly reduce memory pressure for builds involving @@ -160,7 +160,7 @@ optimizations to speed up the processing of header files:</p> <ul> <li><p><em><tt>stat</tt> caching</em>: PTH files cache information obtained via -calls to <tt>stat</tt> that <tt>clang-cc</tt> uses to resolve which files are +calls to <tt>stat</tt> that <tt>clang -cc1</tt> uses to resolve which files are included by <tt>#include</tt> directives. This greatly reduces the overhead involved in context-switching to the kernel to resolve included files.</p></li> |
