https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104397
Bug ID: 104397 Summary: Wrong warning message about global static variable in module(.hpp, .cpp) Product: gcc Version: 9.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: bogdasar1985 at gmail dot com Target Milestone: --- Created attachment 52355 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52355&action=edit Output of "gcc -v -save-temps all-your-options source-file && neofetch --stdout" class.hpp ------------- #ifndef CLASS #define CLASS static int a; class Class { public: Class(); ~Class(); private: int b; int c; }; #endif class.cpp --------------- #include "class.hpp" #include <stdio.h> Class::Class() : b(0), c(0) { a++; printf("%d\n", a); }; Class::~Class() { printf("%d\n", a); a--; } main.cpp ------------- #include "class.hpp" int main() { Class a, b, c, d; return 0; } Compiling that by command: g++ -Wall class.hpp class.cpp main.cpp -o main generate next warning: class.hpp:3:12: warning: ‘a’ defined but not used [-Wunused-variable] 3 | static int a; | ^ which is wrong, because variable a used for output. Output of gcc -v -save-temps all-your-options source-file && neofetch --stdout in attachment file. class.ii ------------ # 1 "class.hpp" # 1 "<built-in>" # 1 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 1 "<command-line>" 2 # 1 "class.hpp" static int a; class Class { public: Class(); ~Class(); private: int b; int c; }; main.ii ------------- # 1 "main.cpp" # 1 "<built-in>" # 1 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 1 "<command-line>" 2 # 1 "main.cpp" #pragma GCC pch_preprocess "class.hpp.gch" int main() { Class a, b, c, d; return 0; }