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Diffstat (limited to 'gcc/doc/standards.texi')
| -rw-r--r-- | gcc/doc/standards.texi | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/gcc/doc/standards.texi b/gcc/doc/standards.texi index 4e9720c..56f6151 100644 --- a/gcc/doc/standards.texi +++ b/gcc/doc/standards.texi @@ -132,10 +132,10 @@ the semantics defined in the standard. To make it act as a conforming freestanding implementation for a freestanding environment, use the option @option{-ffreestanding}; it will then define @code{__STDC_HOSTED__} to @code{0} and not make assumptions about the -meanings of function names from the standard library. To build an OS -kernel, you may well still need to make your own arrangements for -linking and startup. @xref{C Dialect Options,,Options Controlling C -Dialect}. +meanings of function names from the standard library, with exceptions +noted below. To build an OS kernel, you may well still need to make +your own arrangements for linking and startup. +@xref{C Dialect Options,,Options Controlling C Dialect}. GCC does not provide the library facilities required only of hosted implementations, nor yet all the facilities required by C99 of @@ -143,6 +143,16 @@ freestanding implementations; to use the facilities of a hosted environment, you will need to find them elsewhere (for example, in the GNU C library). @xref{Standard Libraries,,Standard Libraries}. +Most of the compiler support routines used by GCC are present in +@file{libgcc}, but there are a few exceptions. GCC requires the +freestanding environment provide @code{memcpy}, @code{memmove}, +@code{memset} and @code{memcmp}. Some older ports of GCC are +configured to use the BSD @code{bcopy}, @code{bzero} and @code{bcmp} +functions instead, but this is deprecated for new ports. +Finally, if @code{__builtin_trap} is used, and the target does +not implement the @code{trap} pattern, then GCC will emit a call +to @code{abort}. + For references to Technical Corrigenda, Rationale documents and information concerning the history of C that is available online, see @uref{http://gcc.gnu.org/readings.html} |