Re: [PATCH 0/2] fail compilation with strcpy

Jeff King [off-list ref] writes:

This is a patch series to address the discussion in the thread at:

  https://public-inbox.org/git/20180713204350.GA16999@sigill.intra.peff.net/

Basically, the question was: can we declare strcpy banned and have a
linter save us the trouble of finding it in review. The answer is yes,
the compiler is good at that. ;)

There are probably as many lists of banned functions as there are coding
style documents. I don't agree with every entry in the ones I've seen.
And in many cases coccinelle is a better choice, because the problem is
not "this function is so bad your patch should not even make it to the
list with it", but "don't do it like A; we prefer to do it like B
instead". And coccinelle does the latter more flexibly and
automatically.

So I tried to pick some obvious and uncontroversial candidates here.
gets() could be another one, but it's mostly banned already (it's out of
the standard, and most libcs mark it with a deprecated attribute).

Note that this needs to be applied on top of 022d2ac1f3 (blame: prefer
xsnprintf to strcpy for colors, 2018-07-13) or it will complain loudly. :)

  [1/2]: introduce "banned function" list
  [2/2]: banned.h: mark strncpy as banned

Hmph, there is no use of any banned function in hex.c, but when
this topic is merged to 'pu', I seem to get this:

$ make DEVELOPER=1 hex.o
GIT_VERSION = 2.18.0.758.g18f90b35b8
    CC hex.o
In file included from git-compat-util.h:1250:0,
                 from cache.h:4,
                 from hex.c:1:
banned.h:14:0: error: "strncpy" redefined [-Werror]
 #define strncpy(x,y,n) BANNED(strncpy)
 
In file included from /usr/include/string.h:630:0,
                 from git-compat-util.h:165,
                 from cache.h:4,
                 from hex.c:1:
/usr/include/x86_64-linux-gnu/bits/string2.h:84:0: note: this is the location of the previous definition
 # define strncpy(dest, src, n) __builtin_strncpy (dest, src, n)
 
cc1: all warnings being treated as errors
Makefile:2279: recipe for target 'hex.o' failed
make: *** [hex.o] Error 1