linkage

I have a few questions about the linkage from the following variables. By examples of 7.1.1/7 of C++03 and experimenting with compilers (Comeau, Clang and GCC), I came to the following linkage kinds: First static , then extern static int a; // (a) extern int a; // (b) valid, 'a' still internal It's clear to me with accordance to section 3.5: (a) implies internal linkage. And (b) also implies internal linkage, because the name "a" is declared static (by (a)). First extern , then static extern int b; // (c) static int b; // (d) invalid! First, (c) implies external linkage. But (d) implies

When I run ldd program I get an output of the form linux-gate.so.1 => (0xb77ae000) libstdc++.so.6 => /lib/libstdc++.so.6 (0xb76bc000) libm.so.6 => /lib/libm.so.6 (0xb7691000) libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb7674000) libc.so.6 => /lib/libc.so.6 (0xb74c2000) /lib/ld-linux.so.2 (0xb77af000) Can you explain the output and the reason linux-gate.so.1 and ld-linux.so.2 show differently than other entries? What are their roles? Petesh I hope that you're not asking about the main entries, which are stating that for the requested library libm.so.6 it was found in the file /lib/libm.so.6 , for

Imagine we have a header foo.h containing the following: #ifndef FOO_H_ #define FOO_H_ namespace foo { constexpr std::string_view kSomeString = "blah"; } #endif // FOO_H_ Is foo::kSomeString guaranteed to have internal linkage in any translation unit that includes foo.h ? Does this vary between C++11 and C++17? In the draft standard [basic.link]/3 says A name having namespace scope has internal linkage if it is the name of [...] a non-inline variable of non-volatile const-qualified type that is neither explicitly declared extern nor previously declared to have external linkage [...] But I don

Yet another static question. I have read the following: What are static variables? file scope and static floats http://msdn.microsoft.com/en-us/library/s1sb61xd.aspx And I still fail to understand the following behavior: I have one h file: // StaticTest.h #include <stdio.h> static int counter = 0; struct A { A () { counter++; printf("In A's ctor(%d)\n", counter); } ~A () { counter--; printf("In A's dtor(%d)\n", counter); } }; static A a; And two cpp files: // StaticTest1.cpp #include "StaticTest.h" int main () { return 0; } And: // StaticTest2.cpp #include "StaticTest.h" The output of the

For example: code1.c / .cpp int a; // ... and so on code2.c / .cpp int a; int main(void) { return 0; } go to compile: $gcc code1.c code2.c # this is fine $ $g++ code1.cpp code2.cpp # this is dead /tmp/ccLY66HQ.o:(.bss+0x0): multiple definition of `a' /tmp/ccnIOmPC.o:(.bss+0x0): first defined here collect2: ld returned 1 exit status Is there any global variable linkage difference between C & C++? CB Bailey It's not strictly legal. int a; is a tentative definition in C. You are allowed multiple tentative definitions and at most one non-tentative definition per translation unit of each object

In C++, putting a function or a variable in an anonymous namespace makes its linkage internal, i. e. the same as declaring it static on a file-level, but idiomatic C++. What about an anonymous namespace within a normal namespace? Does it still guarantee internal linkage? // foo.cpp void func1() { // external linkage } static void func2() { // internal linkage } namespace { void func3() { // internal linkage } } namespace ns1 { void func4() { // external linkage } namespace { void func3() { // still internal linkage? } } } legends2k C++11 (draft N3337) §3.5/4: (emphasis mine) An unnamed

I built boost 1.57.0 in QNX 6.5.0. There is no build error. But some libraries are linked to libboost_system.so specifying relative path. I saved compilation logs. Here is linkage step for boost_thread: "QCC_gpp" -o "bin.v2/libs/thread/build/qcc/release/threading-multi/libboost_thread.so.1.57.0" -shared "bin.v2/libs/thread/build/qcc/release/threading-multi/pthread/thread.o" "bin.v2/libs/thread/build/qcc/release/threading-multi/pthread/once.o" "bin.v2/libs/thread/build/qcc/release/threading-multi/future.o" "bin.v2/libs/system/build/qcc/release/threading-multi/libboost_system.so.1.57.0" -lm So,