del@percheron.ecn.purdue.edu (David A Whittemore) (06/19/91)
i often use sprintf() to append an existing char[] with another:
char line[BIG ARRAY], word[SMALLER ARRAY];
until EOF
fscanf(fp, "%s", word);
sprintf(line, %s %s", line, word);
under Microsoft 5.1 and all other (BSD/SYSV) compilers i have used
this would logically append "line" with "word".
under borland C++ 2.0, however, the line:
sprintf(line, "%s %s", line, word);
acts like:
strcpy(line, word) !
which means it wipes out the existing contents of "line".
example:
char jnk[100];
strcpy(jnk, "hello");
sprintf(jnk, "%s %s", jnk, "world");
yields (under borland): " world"
is this a borland bug, or have i been making some bad
assumptions as to how sprintf() works for years?
ug.
-davids64421@zeus.usq.EDU.AU (house ron) (06/20/91)
del@percheron.ecn.purdue.edu (David A Whittemore) writes: >under borland C++ 2.0, however, the line: > sprintf(line, "%s %s", line, word); >acts like: > strcpy(line, word) ! >which means it wipes out the existing contents of "line". >is this a borland bug, or have i been making some bad >assumptions as to how sprintf() works for years? To quote the ANSI C standard, "If copying takes place between objects that overlap, the behaviour is undefined." -- Regards, Ron House. (s64421@zeus.usq.edu.au) (By post: Info Tech, U.C.S.Q. Toowoomba. Australia. 4350)
gram@uctcs.cs.uct.ac.za (Graham Wheeler) (06/21/91)
In <1991Jun19.003026.21026@noose.ecn.purdue.edu> del@percheron.ecn.purdue.edu (David A Whittemore) writes: >i often use sprintf() to append an existing char[] with another: Why on earth don't you just use strcat? Its a much cheaper operation than a sprintf. -- Graham Wheeler <gram@cs.uct.ac.za> | "That which is weak conquers the strong, Data Network Architectures Lab | that which is soft conquers the hard. Dept. of Computer Science | All men know this; none practise it" University of Cape Town | Lao Tzu - Tao Te Ching Ch.78