Switch C++ code to using C++ version of C headers

[Kurt Schwehr]

To allow C++ code to better manage namespaces and do better error checking, it would be good to switch all C++ code to only use the C++ version of headers.

e.g. changing

#include <string.h>

to

#include <cstring>

The most pivotal location is in cpl_port.h. This file is included by most. The header will require using the preprocessor to switch the headers between C and C++.

cpl_port.h

@@ -125 +125 @@
 /*      Standard include files.                                         */
 /* ==================================================================== */
 
-#include <stdio.h>
-#include <stdlib.h>
-#include <math.h>
-#include <stdarg.h>
-#include <string.h>
-#include <ctype.h>
-#include <limits.h>
+#ifdef __cplusplus
 
-#include <time.h>
+#  include <cctype>
+#  ifdef HAVE_DIRECT_H
+#    include <cdirect>
+#  endif
+#  if defined(HAVE_ERRNO_H)
+#    include <cerrno>
+#  endif
+#  include <climits>
+#  ifdef HAVE_LOCALE_H
+#    include <clocale>
+#  endif
+#  include <cmath>
+#  include <cstdarg>
+#  include <cstdio>
+#  include <cstdlib>
+#  include <cstring>
+#  include <ctime>
 
-#if defined(HAVE_ERRNO_H)
-#  include <errno.h>
-#endif
+#else /* This is C */
 
-#ifdef HAVE_LOCALE_H
-#  include <locale.h>
-#endif
+#  include <ctype.h>
+#  ifdef HAVE_DIRECT_H
+#    include <direct.h>
+#  endif
+#  if defined(HAVE_ERRNO_H)
+#    include <errno.h>
+#  endif
+#  include <limits.h>
+#  ifdef HAVE_LOCALE_H
+#    include <locale.h>
+#  endif
+#  include <math.h>
+#  include <stdarg.h>
+#  include <stdio.h>
+#  include <stdlib.h>
+#  include <string.h>
+#  include <time.h>
 
-#ifdef HAVE_DIRECT_H
-#  include <direct.h>
-#endif
+#endif /* __cplusplus versus c */
 
 #if !defined(WIN32)
 #  include <strings.h>

This will find a large number of the includes that need to be changed, but there are some false matches

find gdal -name \*.cpp -o -name \*.h | xargs egrep \
'["<](assert|float|limits|math|string|stdio|stdlib|signal|time|setjmp|errno|ctype|locale|stdarg|stddef|stdint|uchar|wchar)\.h'\
 | egrep -v 'cpl_config.h|libjpeg|libpng|libtiff|libgeotiff|degrib|libqhull|libjson|zlib|libcsf'

Roughly 110 files.

[Even Rouault]

For the sake of my curiosity, what advantages does it bring concretly ? (examples welcome)

[Kurt Schwehr]

An example courtesy of ​Titus Winters is with abs. My quick demo of the surprise casting through int that can happen...

// no-cname.cc
#include <stdlib.h>
#include <iostream>

using std::cout;

float Foo() { return -1.23f; }

int main () {
  cout << abs(Foo()) << "\n";
  return 0;
}

Surprise...

$ ./no-cname 

1

With the cname header, abs is templated.

// cname.cc
#include <cmath>
#include <iostream>

using std::cout;

float Foo() { return -1.23f; }

int main () {
  cout << std::abs(Foo()) << "\n";
  return 0;
}

More what you might expect...

$ ./cname

1.23

[Even Rouault]

OK thanks

[Even Rouault]

This ticket has been automatically closed because Trac is no longer used for GDAL bug tracking, since the project has migrated to GitHub. If you believe this ticket is still valid, you may file it to ​https://github.com/OSGeo/gdal/issues if it is not already reported there.