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To: <cygwin AT cygwin DOT com>
Subject: Symbol visibility problems with -std=
Date: Wed, 13 May 2020 13:21:23 +0300
Message-ID: <00a001d62910$4120ea20$c362be60$@samsung.com>
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References: <CGME20200513102124eucas1p20b619bf7b82b386c66e935199790b2c1 AT eucas1p2 DOT samsung DOT com>
From: Pavel Fedin via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Pavel Fedin <p DOT fedin AT samsung DOT com>
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Sender: "Cygwin" <cygwin-bounces AT cygwin DOT com>

 Hello everyone!

 While compiling various software packages for Cygwin i notice that very often i have to add something like #define _GNU_SOURCE to
them in order to compile correctly. Meanwhile on Linux they compile with no problems at all. I've narrowed it down to -std=???
option using a simple test case:
--- cut test.cpp ---
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void)
{
        char *p = strdup("hello");

        printf("%s\n", p);
        free(p);
        return 0;
}
--- cut test.cpp ---

$ g++ test.cpp -o test - compiles OK
$ g++ test.cpp -o test -std=c++14 - error: 'strdup' was not declared in this scope; did you mean 'strcmp'?

 By printing out predefined macros (-dM -E) i found out that -std=something option adds " #define __STRICT_ANSI__ 1" to builtin
macros, but removes all *_SOURCE definitions, so _DEFAULT_SOURCE is not triggered any more.
 I've compared the behavior with Linux system. On Linux -std=c++14 also defines __STRICT_ANSI__, but various *_SOURCE macros are not
omitted.
 Isn't this a Cygwin bug? By the way, clang does not suffer from this problem.

Kind regards,
Pavel Fedin
Senior Engineer
Samsung Electronics Research center Russia


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