¿Cómo puedo activar de forma portátil el soporte de archivos grandes?
Actualmente estoy escribiendo un programa en C que lee y escribe archivos que pueden tener más de 2 GiB de tamaño. En linuxfeature_test_macros(7) especifica:
_LARGEFILE64_SOURCE
Expose definitions for the alternative API specified by the LFS (Large File Summit) as a "tran‐
sitional extension" to the Single UNIX Specification. (See ⟨http://opengroup.org/platform
/lfs.html⟩) The alternative API consists of a set of new objects (i.e., functions and types)
whose names are suffixed with "64" (e.g., off64_t versus off_t, lseek64() versus lseek(), etc.).
New programs should not employ this interface; instead _FILE_OFFSET_BITS=64 should be employed.
_FILE_OFFSET_BITS
Defining this macro with the value 64 automatically converts references to 32-bit functions and
data types related to file I/O and file system operations into references to their 64-bit coun‐
terparts. This is useful for performing I/O on large files (> 2 Gigabytes) on 32-bit systems.
(Defining this macro permits correctly written programs to use large files with only a recompi‐
lation being required.) 64-bit systems naturally permit file sizes greater than 2 Gigabytes,
and on those systems this macro has no effect.
¿Está esto garantizado para ser portátil?
Solaris sugiere encompilar(5):
Applications can be compiled in the large file compilation
environment by using the following methods:
o Use the getconf(1) utility with one or more of the
arguments listed in the table below. This method is
recommended for portable applications.
____________________________________________________________
| argument | purpose |
|__________________|________________________________________|
| LFS_CFLAGS | obtain compilation flags necessary to|
| | enable the large file compilation|
| | environment |
| LFS_LDFLAGS | obtain link editor options |
| LFS_LIBS | obtain link library names |
| LFS_LINTFLAGS | obtain lint options |
|__________________|________________________________________|
o Set the compile-time flag _FILE_OFFSET_BITS to 64
before including any headers. Applications may com-
bine objects produced in the large file compilation
environment with objects produced in the transi-
tional compilation environment, but must be careful
with respect to interoperability between those
objects. Applications should not declare global
variables of types whose sizes change between com-
pilation environments.
¿Esto es portátil? En mi máquina linux, pasando estas llaves agetconf no dará salida a nada. (Lo que significa que las llaves existen).
¿Hay algún enfoque portátil?