HLASM: V1R6 Language Ref

WXTRN instructionWXTRN instructionThe WXTRN statement identifies “weak external” symbols referred to in a sourcemodule but defined in another source module. The WXTRN instruction differsfrom the EXTRN instruction (see “EXTRN instruction” on page 188) as follows:v The EXTRN instruction causes the linker to automatically search libraries (ifautomatic library call is in effect) to find the module that contains the externalsymbols that you identify in its operand field. If the module is found, linkageaddresses are resolved; the module is then linked to your module, whichcontains the EXTRN instruction.v The WXTRN instruction suppresses automatic search of libraries. The linker onlyresolves the linkage addresses if the external symbols that you identify in theWXTRN operand field are defined:– In a module that is linked and loaded along with the object moduleassembled from your source module, or– In a module brought in from a library because of the presence of an EXTRNinstruction in another module linked and loaded with yours.|,►►sequence_symbolWXTRN ▼ external_symbol,▼►◄PART( external_symbol )|||sequence_symbolis a sequence symbol.external_symbolis a relocatable symbol that is not:v Used as the name entry of a source statement in the source module in whichit is definedPART(external_symbol)external_symbol is a relocatable symbol as described above, that also:v Is a reference to a part as defined on the CATTR instruction.The external symbols identified by a WXTRN instruction have the same propertiesas the external symbols identified by the EXTRN instruction. However, the typecode assigned to these external symbols differs.V-Type Address Constant: If a symbol, specified in a V-type address constant, isalso identified by a WXTRN instruction, it is assigned the same ESD type code asthe symbol in the WXTRN instruction, and is treated by the linkage editor as aweak external symbol.If an external symbol is identified by both an EXTRN and WXTRN instruction inthe same source module, the first declaration takes precedence, and subsequentdeclarations are flagged with diagnostic messages.Chapter 5. Assembler instruction statements 227