C Struct Order of Members -

i'm taking on piece of code..c programming in linux. did small change struct

typedef struct {   unsigned int a1;   ..   ..   ..   float f1;   unsigned int a2;   unsigned int a3;    unsigned int offending; // shifted } test;

i shifted unsigned int offending before float f1, this:

typedef struct {   unsigned int a1;   ..   ..   ..   unsigned int offending;   float f1;   unsigned int a2;   unsigned int a3;   } test;

and code crashes... problem?

is order of members of c struct important?

what problem? depend on rest of code, , else did.

no, order of members of struct not intrinsically important. made when other code depends on it.

possible causes (not exhaustive):

you didn't recompile , there external linkage on struct or aspect of it.
by moving member changed alignment of other members and/or sizeof() struct, , didn't compensate that.
there literal constant or macro somewhere size or offset depends on struct.
there faulty code never failed before because of change in memory layout.
the struct used somewhere part of struct or union, , problem related that.
there list initialisation using {} no longer matches member order.

you should provide details of how crashes. otherwise guesswork. , perhaps then.

edit: ht @jens.

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