Alexey Skidanov <skidanovalexey@xxxxxxxxx> writes: > Do you mean, once I break the ODR theÂfurther behaviour is unexpected? > > You are right. I break it. And I would like to get linker/loader error/warning > as I get linkingÂtwo object files with the same global variable defined in each > file ( "Symbol zzz already defined" or something like that). You will already get an error for a multiple definition. What is happening here is that you have two different instances of a variable or function with vague linkage which originated in two different sources. Because g++ uses the Borland linking model by default, in which symbols with vague linkage are duplicated in each .o file which uses them, the linker can not easily determine that in this case the symbols are an ODR violation rather than an ordinary duplication. The gold linker does implement a --detect-odr-violations option. Whenever it sees a symbol with vague linkage appearing more than once, such that the two instances have different sizes or symbol types, it checks the debug info for the symbols. If they originate from different files, it issues a warning. This approach works fairly well if the object files are compiled with debugging information and without optimization. When optimization is used, there are false positives due to confusion due to inlined functions. Ian
