diff options
Diffstat (limited to 'gcc/doc/extend.texi')
| -rw-r--r-- | gcc/doc/extend.texi | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index d737617a..7073c90 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -2671,6 +2671,31 @@ SRAM. The function will be put into a specific section named @code{.l1.text}. With @option{-mfdpic}, callers of such functions will use an inlined PLT. +@item leaf +@cindex @code{leaf} function attribute +Calls to external functions with this attribute must return to the current +compilation unit only by return or by exception handling. In particular, leaf +functions are not allowed to call callback function passed to it from current +compilation unit or directly call functions exported by the unit or longjmp +into the unit. Still leaf function might call functions from other complation +units and thus they are not neccesarily leaf in the sense that they contains no +function calls at all. + +The attribute is intended for library functions to improve dataflow analysis. +Compiler takes the hint that any data not escaping current compilation unit can +not be used or modified by the leaf function. For example, function @code{sin} +is leaf, function @code{qsort} is not. + +Note that the leaf functions might invoke signals and signal handlers might be +defined in the current compilation unit and use static variables. Only +compliant way to write such a signal handler is to declare such variables +@code{volatile}. + +The attribute has no effect on functions defined within current compilation +unit. This is to allow easy merging of multiple compilation units into one, +for example, by using the link time optimization. For this reason the +attribute is not allowed on types to annotate indirect calls. + @item long_call/short_call @cindex indirect calls on ARM This attribute specifies how a particular function is called on |