Hello

-
Hello,

I'm translating some C code to Delphi and found something that surprise me...is it logical that this code compiles ?

{code}
#include
#include

void test();

void test2() {
test();
}

void test(char *msg) {
printf("test called '%s' (%d)\n", msg, strlen(msg));
}

void main() {
test2();
}
{code}

and the result is
test called 'test' (4)

tested with gcc under Ubuntu

thanks

Comments

  1. Dorin DuminicaNovember 1, 2017 at 3:18 PM

    pretty weird, tested gcc on mac, it builds, with some warnings

    testc.c:11:42: warning: format specifies type 'int' but the argument has type 'unsigned long' [-Wformat]
    printf("test called '%s' (%d)\n", msg, strlen(msg));
    ~~ ^~~~~~~~~~~
    %lu
    testc.c:14:1: warning: return type of 'main' is not 'int' [-Wmain-return-type]
    void main() {
    ^
    testc.c:14:1: note: change return type to 'int'
    void main() {
    ^~~~
    int

    nothing about calling test without an arg

    running the build results in:

    Segmentation fault: 11

    ReplyDelete
  2. Paul TOTHNovember 1, 2017 at 3:21 PM

    note that I've put the call to test() in test2() because a direct call from main() raise an error "too few argements to function 'test'"

    ReplyDelete
  3. Dorin DuminicaNovember 1, 2017 at 3:23 PM

    yes, saw it, on my end, it looks like it's using clang, regardless, it builds tho it shouldn't

    ReplyDelete
  4. David SchwartzNovember 1, 2017 at 9:14 PM

    You declared both the prototype and the call as taking no parameters. Then you declared the body of the function as taking a pointer.

    If there's a compiler bug, it would be either:

    (1) not complaining that the declaration of test with a non-empty argument list hides or in some way overrides the one with an empty argument list; or

    (2) that it is using the version of test with an argument and creating a stack frame with an implied argument while calling the function that takes zero arguments.

    Given how loosey-goosey the c programming language has always been when it comes to various kinds of undocumented "shorthand notations", this doesn't surprise me a bit.

    Interestingly, Pascal has allowed you to call procs defined with parameter lists with a call having no parameters forever. Try it in Delphi ... it might not even generate hint or warning.

    ReplyDelete
  5. Евгений СавинNovember 1, 2017 at 9:54 PM

    ideone gives error as expected ideone.com - Ideone.com

    ReplyDelete
  6. Daniela OsterhagenNovember 2, 2017 at 12:26 AM

    This is C, everything compiles. ;-)
    Your function prototype test, which is used for the call in test2, does not have a parameter, so it compiles. Then it gets redefined as having a parameter. This should cause a compile error, but since it is never called after the definition, it apparently doesn't.

    ReplyDelete
  7. Asbjørn HeidNovember 2, 2017 at 12:36 AM

    Daniela Osterhagen So a linker issue then.

    ReplyDelete
  8. Paul TOTHNovember 2, 2017 at 1:29 AM

    ok, the error is in this project

    https://github.com/fogleman/Craft/search?q=db_worker_start

    ReplyDelete

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