Reliable detection of strerror_r variants

cmake/config.h.cmake

@@ -27,6 +27,9 @@
 // Define if you have the strerror_r function.
 #cmakedefine EXV_HAVE_STRERROR_R
 
+// Define if the strerror_r function returns char*.
+#cmakedefine EXV_STRERROR_R_CHAR_P
+
 // Define to enable the Windows unicode path support.
 #cmakedefine EXV_UNICODE_PATH
 

cmake/generateConfigFile.cmake

@@ -1,4 +1,5 @@
 include(CheckIncludeFile)
+include(CheckCXXSourceCompiles)
 
 # Note that the scope of the EXV_ variables in local
 if (${EXIV2_ENABLE_WEBREADY})
@@ -28,6 +29,14 @@ check_function_exists( mmap     EXV_HAVE_MMAP )
 check_function_exists( munmap   EXV_HAVE_MUNMAP )
 check_function_exists( strerror_r   EXV_HAVE_STRERROR_R )
 
+check_cxx_source_compiles( "
+#include <string.h>
+int main() {
+    char buff[100];
+    const char* c = strerror_r(0,buff,100);
+    return 0;
+}" EXV_STRERROR_R_CHAR_P )
+
 check_include_file( "unistd.h"  EXV_HAVE_UNISTD_H )
 check_include_file( "memory.h"  EXV_HAVE_MEMORY_H )
 check_include_file( "process.h" EXV_HAVE_PROCESS_H )

src/futils.cpp

@@ -53,14 +53,6 @@
 #include <algorithm>
 #include <stdexcept>
 
-#ifdef EXV_HAVE_STRERROR_R
-#if defined(__GLIBC__) && defined(_GNU_SOURCE)
-extern char *strerror_r(int errnum, char *buf, size_t n);
-#else
-extern int strerror_r(int errnum, char *buf, size_t n);
-#endif
-#endif
-
 namespace Exiv2 {
     const char* ENVARDEF[] = {"/exiv2.php", "40"}; //!< @brief default URL for http exiv2 handler and time-out
     const char* ENVARKEY[] = {"EXIV2_HTTP_POST", "EXIV2_TIMEOUT"}; //!< @brief request keys for http exiv2 handler and time-out
@@ -348,7 +340,7 @@ namespace Exiv2 {
         std::ostringstream os;
 #ifdef EXV_HAVE_STRERROR_R
         const size_t n = 1024;
-#if defined(__GLIBC__) && defined(_GNU_SOURCE)
+#ifdef EXV_STRERROR_R_CHAR_P
         char *buf = 0;
         char buf2[n];
         std::memset(buf2, 0x0, n);