diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 33 |
1 files changed, 28 insertions, 5 deletions
@@ -64059,17 +64059,40 @@ as its value. .coNP Macro @ sizeof .synb -.mets (sizeof << type-syntax ) +.mets (sizeof < type-syntax <> [ object-expr ]) .syne .desc The macro .code sizeof calculates the size of the FFI type denoted by +.codn type-syntax . + +The +.meta type-syntax +expression is compiled to a type using +.codn ffi-type-compile . +The +.meta object-expr +expression is evaluated to an object value. + +If .code type-syntax -at macro-expansion time, and produces that -integer value as its expansion, such that there is no -run-time computation. It uses the -.code ffi-sizeof +denotes a variable length type, and the +.meta object-expr +argument is present, then a +.I "dynamic size" is computed: the actual number of bytes required to store +that object value as a foreign representation of the specified variable length +type. + +The +.code sizeof +macro arranges for the size calculation to be carried out at macro-expansion +time, if possible, so that the +.code sizeof +form is replaced by an integer constant. This is possible when the +.meta object-expr +is omitted, or if it is a constant expression according to the +.code constantp function. .coNP Macro @ alignof |