c++ - One definition rule warning -

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i have been bitten nasty "one definition rule" violation. afraid of having lots of subtle bugs in projects.

for example, following program result in null pointer dereference visual studio 2015:

source1.cpp: ---------- struct s {     double d = 0; };  void foo() {     s s; }   source2.cpp: ----------- struct s {     int = 0; };  int main() {      int value = 5;     int& valueref = value;     s s;           // valueref erased due s::d initialization source1.cpp      valueref++;    // crash }

this compiles no warnings.

it's nasty because source2.cpp doesn't use source1.cpp. if remove source1.cpp project, still compiles, , there no problem anymore.

in large projects, seems hard ensure no cpp file "locally" define struct or class defined name.

i have classes such point, serie, state, item, ... though ok in small cpp files, realize it's not safe.

is there compiler warning catch such bugs ? if not, best practices avoid odr violation ?

in particular case, @ bottom odr violation (which leads problem observing) implicitly-defined inline constructor of class s. program has 2 non-matching versions of inline s::s() function, can seen odr violation induced original odr violation (i.e. same class defined differently).

it difficult implementation "see" error in current approach c++ compilation infrastructure. of course, possible sufficient effort.

in case in order make error "visible" can explicitly declare , define class constructor non-inline function empty body. presence of 2 non-inline s::s() trigger linker error.

understandably, might see overly artificial measure, unacceptable in cases since might change "aggregate" status of class.


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