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| -rw-r--r-- | docs/Glibc_vs_uClibc_Differences.txt | 73 |
1 files changed, 72 insertions, 1 deletions
diff --git a/docs/Glibc_vs_uClibc_Differences.txt b/docs/Glibc_vs_uClibc_Differences.txt index 16608abdf..c461e06c2 100644 --- a/docs/Glibc_vs_uClibc_Differences.txt +++ b/docs/Glibc_vs_uClibc_Differences.txt @@ -1,4 +1,4 @@ -uClibc and Glibc are not the same -- there are a number of differences which + uClibc and Glibc are not the same -- there are a number of differences which may or may not cause you problems. This document attempts to list these differences and, when completed, will contain a full list of all relevant differences. @@ -54,3 +54,74 @@ encrypt_r, since these are not required by SuSv3. 14) uClibc directly uses the linux kernel's arch specific 'stuct stat'. 15) Add other things here as they come up...... + + + +****************************** Manuel's Notes ****************************** + +Some general comments... + +The intended target for all my uClibc code is ANSI/ISO C99 and SUSv3 +compliance. While some glibc extensions are present, many will eventually +be configurable. Also, even when present, the glibc-like extensions may +differ slightly or be more restrictive than the native glibc counterparts. +They are primarily meant to be porting _aides_ and not necessarily +drop-in replacements. + +Now for some details... + +time functions +-------------- +1) Leap seconds are not supported. +2) /etc/timezone and the whole zoneinfo directory tree are not supported. + To set the timezone, set the TZ environment variable as specified in + http://www.opengroup.org/onlinepubs/007904975/basedefs/xbd_chap08.html + or you may also create an /etc/TZ file of a single line, ending with a + newline, containing the TZ setting. For example + echo CST6CDT > /etc/TZ +3) Currently, locale specific eras and alternate digits are not supported. + They are on my TODO list. + +wide char support +----------------- +1) The only multibyte encoding to be supported will be UTF-8. The various + ISO-8859-* encodings will be (optionally) supported. The internal + representation of wchar's is assumed to be 31 bit unicode values in + native endian representation. Also, the underlying char encoding is + assumed to match ASCII in the range 0-0x7f. +2) In the C locale, uClibc's mb<->wc conversion functions map 0x80-CHAR_MAX + onto their wide/narrow equivalents. glibc's conversion functions treat + them as illegal. + +locale support +-------------- +1) The target for support is SUSv3 locale functionality. While nl_langinfo + has been extended, similar to glibc, it only returns values for related + locale entries. +2) The locale code is not cross-compiler friendly. This should be fixed soon. +3) Currently, collation support is being implemented. + +stdio +----- +1) For printf, %a, %A, and floating point locale-specific grouping are not + yet implemented. Also, conversion of large magnitude floating-point values + suffers a loss of precision due to the algorithm used. The conversion + function was written before uClibc had proper semi-numerical macros/functions. + This code is slated to be rewritten after the i10n/i18n work is completed. +2) uClibc's printf is much stricter than glibcs, especially regarding positional + args. The entire format string is parsed first and an error is returned if + a problem is detected. Also, currently at most 10 positional args are allowed + although this is configurable. +3) BUFSIZ is currently 256. No attempt is made at automatic tuning of internal + buffer sizes for stdio streams. In fact, the stdio code in general sacrifices + sophistication/performace for minimal size. +4) uClibc allows glibc-like custom printf functions. However, while not + currently checked, the specifier must be <= 0x7f. +5) uClibc allows glibc-like custom streams. However, no in-buffer seeking is + done. +6) uClibc's scanf still needs work. +7) The functions fcloseall() and __fpending() can behave differently than their + glibc counterparts. + + +More to follow as I think of it... |