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gcc extern c error Viburnum, Missouri

But worse thing is that the definition in the cpp_main.h differs from that in the cpp_main.cpp in the returned type (void vs int). Related 65extern inline595How do I use extern to share variables between source files in C?1Are there any drawbacks to declaring variables in header files without the “extern” keyword?1What's the point of To "share a variable between modules", just: a) Declare the "extern" (EXAMPLE: in "a.h") b) Define the variable (EXAMPLE: in "a.cpp") 2. Tools Insider University Program Groups Corporate Citizenship TI University Program Russian E2E (сообщество E2E) Japanese E2E (日本語コミュニティ) Learn E2E Launch Your Design Motor Drive & Control Videos More Cancel MSP Low-Power

This is free software; see the source for copying conditions. ok then plz give a thought to this one also………. #include int main(void) { int foo(); int foo(); int foo(){} return 0; } why it is giving an error as foo() I am confused here. But we notice the actual definition of the function only once (i.e.

The time now is 09:08 PM. share|improve this answer answered Aug 28 '13 at 17:57 jhauris 518210 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google Sign Advertise with us! It is because extern int is declaration, not definition.

Your explanation was clear as crystal! and all tentative definitions are combined to actual ones when the compiler finds the corresponding real definition and if it does not it initializes it to default value. gt #include extern int a; int main() { extern int a; int a=34; printf("%d",a); return 0; } why this code is showing error?? I have thse source files: a.c: Code: #define MAIN #include int main(){ B = calloc(1,200); strcpy( B, "Hello" ); printf("B: %s\n", B ); SUB(); printf("B: %s\n", B ); return; }

That used to be necessary in very, very old C compilers. OK, now I've removed the #include cpp_main.h from the main() file and compiled it.. Thanks Alireza What is the "actual definition of the function"? The default variable name in make for C++ compiler is CXX (and CXXFLAGS for C++ compiler-specific flags). –MadScientist Jan 22 '14 at 21:28 add a comment| 1 Answer 1 active oldest

Therefore, we put extern explicitly for C variables when we want to declare them without defining them. Thanks very much! Browse other questions tagged c or ask your own question. However, your solution fixes the problem on the wrong end.

The C++ header, where C___plusplus is defined has the function declarations in an extern "C" block. int var; Here, an integer type variable called var has been declared as well as defined. (remember that definition is the super set of declaration). About Us! What you probably want is just "extern char *B".

jay #include int var; int var; int var; int main(void) { int var = 564 ; printf("%d n",var); return 0; } why it is not giving any error as var is Also it's not because I didn't have a semi-colon after the 'extern' decleration. error : ‘var’ has both ‘extern’ and initializer int main(void) { extern int var = 0; var = 10; return 0; } any one explain why it is happened?? Example 2: extern int var; int main(void) { return 0; } Analysis: This program is compiled successfully.

Thanks /* Paste your code here (You may delete these lines if not writing code) */ a user Thank you vikash very well explained. Let us first take the easy case. Join them; it only takes a minute: Sign up Compiling program containing extern “C” up vote 3 down vote favorite 1 I'm trying to use a makefile to compile a program Essentially, the var isn’t allocated any memory.

The compiler is including that file instead of the standard one from /usr/include. –Ziffusion Aug 28 '13 at 20:51 1 Ah. I'm sure that you want to have some take away from the reading of this post. Rose Robinson Thanks for a great article! share|improve this answer edited Aug 29 '13 at 14:36 answered Aug 28 '13 at 18:13 Ziffusion 5,68811130 @JonP.Harris The strange thing is, as I mentioned I have not written

Durgesh PS: thats why Jay is not getting error Durgesh my dear friend int var ; is not a definition its an tentative definition . I use Linux and am compiling with gcc/g++ 4.3.2 however I'm coming across a strange problem that I just can't resolve. Arpit Jain If you like your function definition then have to look on this program. #include void go(void (*foo)()){ foo(); // to access foo from outside you need to use function Enisha Good explaination !!

the code for test1.c /* #include int main(void) { extern int var=1; printf("\nThe value of var is %d\n",var); return 0; } */ and the o/p at compilation time $ gcc test1.c Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff. © Copyright 1995-2016 Texas Instruments Incorporated. or "test.c" has definition of ‘a' inside #include extern int a; int main() { extern int a; //looks for a outside of its scope(main function here) int a=34; printf("%d",a); return 0; melkiy: I was playing round with the return type and forgot to put it back before quoting the code here in the forum.

Thanks in Advance Aarthi Excellent explanation. Otherwise it's another problem. Reply Cancel Cancel Reply Suggest as Answer Use rich formatting Expert 2065 points Rick Kimball Jul 28, 2014 1:08 AM In reply to Jens-Michael Gross: I'm going to stop talking about parthi hi, this details easy 2 understand… great explanation thanku parthi Rudra Pratap Excellent explanation.

extern int foo(int arg1, char arg2); Same is the case with the definition of a C function (Definition of a C function means writing the body of the function). Shailesh Thakurdesai Aug 4, 2016 Air quality monitors and smoke detectors put on a new face Air quality monitors are not... > Not Answered extern "C" not understood by g++ ? This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. Introduction to Linux - A Hands on Guide This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started

And it won’t work for CCS and IAR, where the SFRs are linked by the linker and the compiler has to generate relocation entries that have to be resolved by the I feel that it more interesting and information than the previous case where extern is present by default with C functions. second paragraph last third line. "variable/function can be declared any number of times but it can be defined only once. (Remember the basic principle that you can’t have two locations of