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Commitdbbba52

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Start using flexible array members
Flexible array members are a C99 feature that avoids "cheating" in thedeclaration of variable-length arrays at the end of structs. WithAutoconf support, this should be transparent for older compilers.We start with one use in gist.h because gcc 4.6 started to raise awarning there. Over time, it can be expanded to other places in thesource, but they will likely need some review of sizeof and offsetofusage. The current change in gist.h appears to be safe in thisregard.
1 parent78475b0 commitdbbba52

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4 files changed

+82
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lines changed

4 files changed

+82
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‎configure

Lines changed: 71 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -14954,6 +14954,77 @@ _ACEOF
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fi
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{ $as_echo "$as_me:$LINENO: checking for flexible array members" >&5
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$as_echo_n "checking for flexible array members... " >&6; }
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if test "${ac_cv_c_flexmember+set}" = set; then
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$as_echo_n "(cached) " >&6
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else
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cat >conftest.$ac_ext <<_ACEOF
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/* confdefs.h. */
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_ACEOF
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cat confdefs.h >>conftest.$ac_ext
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cat >>conftest.$ac_ext <<_ACEOF
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/* end confdefs.h. */
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#include <stdlib.h>
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#include <stdio.h>
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#include <stddef.h>
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struct s { int n; double d[]; };
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int
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main ()
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{
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int m = getchar ();
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struct s *p = malloc (offsetof (struct s, d)
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+ m * sizeof (double));
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p->d[0] = 0.0;
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return p->d != (double *) NULL;
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;
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return 0;
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}
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_ACEOF
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rm -f conftest.$ac_objext
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if { (ac_try="$ac_compile"
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case "(($ac_try" in
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*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
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*) ac_try_echo=$ac_try;;
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esac
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eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
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$as_echo "$ac_try_echo") >&5
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(eval "$ac_compile") 2>conftest.er1
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ac_status=$?
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grep -v '^ *+' conftest.er1 >conftest.err
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rm -f conftest.er1
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cat conftest.err >&5
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$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
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(exit $ac_status); } && {
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test -z "$ac_c_werror_flag" ||
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test ! -s conftest.err
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} && test -s conftest.$ac_objext; then
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ac_cv_c_flexmember=yes
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else
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$as_echo "$as_me: failed program was:" >&5
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sed 's/^/| /' conftest.$ac_ext >&5
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ac_cv_c_flexmember=no
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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fi
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{ $as_echo "$as_me:$LINENO: result: $ac_cv_c_flexmember" >&5
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$as_echo "$ac_cv_c_flexmember" >&6; }
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if test $ac_cv_c_flexmember = yes; then
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cat >>confdefs.h <<\_ACEOF
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#define FLEXIBLE_ARRAY_MEMBER /**/
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_ACEOF
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else
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cat >>confdefs.h <<\_ACEOF
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#define FLEXIBLE_ARRAY_MEMBER 1
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_ACEOF
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fi
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{ $as_echo "$as_me:$LINENO: checking for signed types" >&5
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$as_echo_n "checking for signed types... " >&6; }
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if test "${pgac_cv_c_signed+set}" = set; then

‎configure.in

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1110,6 +1110,7 @@ AC_C_BIGENDIAN
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AC_C_CONST
11111111
PGAC_C_INLINE
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AC_C_STRINGIZE
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AC_C_FLEXIBLE_ARRAY_MEMBER
11131114
PGAC_C_SIGNED
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AC_C_VOLATILE
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PGAC_C_FUNCNAME_SUPPORT

‎src/include/access/gist.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -144,7 +144,7 @@ typedef struct GISTENTRY
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typedefstruct
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{
146146
int32n;/* number of elements */
147-
GISTENTRYvector[1];/* variable-length array */
147+
GISTENTRYvector[FLEXIBLE_ARRAY_MEMBER];
148148
}GistEntryVector;
149149

150150
#defineGEVHDRSZ(offsetof(GistEntryVector, vector))

‎src/include/pg_config.h.in

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -61,6 +61,15 @@
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(--enable-thread-safety) */
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#undef ENABLE_THREAD_SAFETY
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/* Define to nothing if C supports flexible array members, and to 1 if it does
65+
not. That way, with a declaration like `struct s { int n; double
66+
d[FLEXIBLE_ARRAY_MEMBER]; };', the struct hack can be used with pre-C99
67+
compilers. When computing the size of such an object, don't use 'sizeof
68+
(struct s)' as it overestimates the size. Use 'offsetof (struct s, d)'
69+
instead. Don't use 'offsetof (struct s, d[0])', as this doesn't work with
70+
MSVC and with C++ compilers. */
71+
#undef FLEXIBLE_ARRAY_MEMBER
72+
6473
/* float4 values are passed by value if 'true', by reference if 'false' */
6574
#undef FLOAT4PASSBYVAL
6675

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