| Message ID | 7c2c6f060393abf3ac831837e4bf8ed366c2fa69.1572596278.git.congdanhqx@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Linux with musl libc improvement | expand |
On Fri, Nov 01, 2019 at 03:25:10PM +0700, Doan Tran Cong Danh wrote: > From commit 79444c9294, ("utf8: handle systems that don't write BOM for > UTF-16", 2019-02-12), we're supporting those systems with iconv that > omits BOM with: > > make ICONV_OMITS_BOM=Yes > > However, typing the flag all the time is cumbersome and error-prone. > > Add a checking into configure script to detect this flag automatically. s/checking/check/ The patch looks good to me, though my knowledge of both iconv and autoconf is relatively lacking. I'll assume it works on your system, though. :) One thing I noticed: > + v = (unsigned char)(out[0]) + (unsigned char)(out[1]); > + return v != 0xfe + 0xff; I wondered at first why not just: return v[0] != 0xfe || v[1] != 0xff; but the answer is that you are catching BOMs of either endianness. We might at some point need to distinguish the two, but I think for the purposes of OMITS_BOM, we don't have to care. So we can worry about that later (if ever). -Peff
On 2019-11-01 12:56:57 -0400, Jeff King wrote: > On Fri, Nov 01, 2019 at 03:25:10PM +0700, Doan Tran Cong Danh wrote: > > + v = (unsigned char)(out[0]) + (unsigned char)(out[1]); > > + return v != 0xfe + 0xff; > > I wondered at first why not just: > > return v[0] != 0xfe || v[1] != 0xff; > > but the answer is that you are catching BOMs of either endianness. We > might at some point need to distinguish the two, Yes, it's about catching BOM of either endianess. To distinguish between LE and BE, it'll be better to use AC_C_BIGENDIAN instead (it's friendlier for cross-compiling). Anyway, we couldn't compare out[0] and out[1] with 0xf{e,f} directly because char could be either signed (-2 and -1) or unsigned (0xfe, 0xff). We must cast it to unsigned char (required to be 8 bits by POSIX), then let the integer promotion promote it to int (at least 16 bits).
diff --git a/configure.ac b/configure.ac index a43b476402..ecba7e6e51 100644 --- a/configure.ac +++ b/configure.ac @@ -844,12 +844,61 @@ AC_MSG_CHECKING([for old iconv()]) AC_COMPILE_IFELSE([OLDICONVTEST_SRC], [AC_MSG_RESULT([no])], [AC_MSG_RESULT([yes]) + AC_DEFINE(HAVE_OLD_ICONV, 1) OLD_ICONV=UnfortunatelyYes]) GIT_UNSTASH_FLAGS($ICONVDIR) GIT_CONF_SUBST([OLD_ICONV]) +# +# Define ICONV_OMITS_BOM if you are on a system which +# iconv omits bom for utf-{16,32} +if test -z "$NO_ICONV"; then +AC_CACHE_CHECK([whether iconv omits bom for utf-16 and utf-32], + [ac_cv_iconv_omits_bom], +[ +old_LIBS="$LIBS" +if test -n "$NEEDS_LIBICONV"; then + LIBS="$LIBS -liconv" +fi + +AC_RUN_IFELSE( + [AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT + #include <iconv.h> + #ifdef HAVE_OLD_ICONV + typedef const char *iconv_ibp; + #else + typedef char *iconv_ibp; + #endif + ], + [[ + int v; + iconv_t conv; + char in[] = "a"; iconv_ibp pin = in; + char out[20] = ""; char *pout = out; + size_t isz = sizeof in; + size_t osz = sizeof out; + + conv = iconv_open("UTF-16", "UTF-8"); + iconv(conv, &pin, &isz, &pout, &osz); + iconv_close(conv); + v = (unsigned char)(out[0]) + (unsigned char)(out[1]); + return v != 0xfe + 0xff; + ]])], + [ac_cv_iconv_omits_bom=no], + [ac_cv_iconv_omits_bom=yes]) + +LIBS="$old_LIBS" +]) +if test "x$ac_cv_iconv_omits_bom" = xyes; then + ICONV_OMITS_BOM=Yes +else + ICONV_OMITS_BOM= +fi +GIT_CONF_SUBST([ICONV_OMITS_BOM]) +fi + ## Checks for typedefs, structures, and compiler characteristics. AC_MSG_NOTICE([CHECKS for typedefs, structures, and compiler characteristics]) #
From commit 79444c9294, ("utf8: handle systems that don't write BOM for UTF-16", 2019-02-12), we're supporting those systems with iconv that omits BOM with: make ICONV_OMITS_BOM=Yes However, typing the flag all the time is cumbersome and error-prone. Add a checking into configure script to detect this flag automatically. Signed-off-by: Doan Tran Cong Danh <congdanhqx@gmail.com> --- configure.ac | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+)