fix aliasing violations in fgetpos/fsetpos

add a member of appropriate type to the fpos_t union so that accesses
are well-defined. use long long instead of off_t since off_t is not
always exposed in stdio.h and there's no namespace-clean alias for it.

access is still performed using pointer casts rather than by naming
the union member as a matter of style; to the extent possible, the
naming of fields in opaque types defined in the public headers is not
treated as an API contract with the implementation. access via the
pointer cast is valid as long as the union has a member of matching
type.

diff --git a/include/stdio.h b/include/stdio.h
index 7c4f9ee499bcf50bca913777c03c03ca35cfce29..afadd9124a847dfdf6b407049c7e0a32d9f389f4 100644 (file)
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -49,6 +49,7 @@ extern "C" {
 
 typedef union _G_fpos64_t {
        char __opaque[16];
+       long long __lldata;
        double __align;
 } fpos_t;
 

diff --git a/src/stdio/fgetpos.c b/src/stdio/fgetpos.c
index c3fa0eb0af42982153d5222a7b76e51f941e941e..6eb361e1986b720a37f02932c4f32c52cc3a0b12 100644 (file)
--- a/src/stdio/fgetpos.c
+++ b/src/stdio/fgetpos.c
@@ -4,7 +4,7 @@ int fgetpos(FILE *restrict f, fpos_t *restrict pos)
 {
        off_t off = __ftello(f);
        if (off < 0) return -1;
-       *(off_t *)pos = off;
+       *(long long *)pos = off;
        return 0;
 }
 

diff --git a/src/stdio/fsetpos.c b/src/stdio/fsetpos.c
index 5d76c8cd5dee42c2b946774e6a0e456db7512a84..6310424ed4caca93bbb9a79dce646f8894eaea47 100644 (file)
--- a/src/stdio/fsetpos.c
+++ b/src/stdio/fsetpos.c
@@ -2,7 +2,7 @@
 
 int fsetpos(FILE *f, const fpos_t *pos)
 {
-       return __fseeko(f, *(const off_t *)pos, SEEK_SET);
+       return __fseeko(f, *(const long long *)pos, SEEK_SET);
 }
 
 LFS64(fsetpos);