------- Additional Comments From kmk at ssl dot org 2005-02-27 12:48 ------- I'm not sure I understand why it is thought that the C standard forbids the conversion I'm talking about here. In fact, the final committee draft of the ISO C standard that I have appears to be silent about the issue of multi-level pointer conversions entirely. As noted by F. Hueffner, conversion rules are made quite explicit in the C++ standard:
In ISO/IEC 14882 4.4.4, multi-level pointer conversions are explicitly constrained by restricting automatic qualifier promotion to only those levels for which _all_ preceding levels are const. The example that follows the paragraph furthers the point by noting: "if a program could assign a pointer of type T** to a pointer of type const T**...a program could inadvertently modify a const object." Absolutely. But that's not what I'm talking about. GCC issues an unsuppressible warning when a conversion is made between: char *const *object --> const char *const *object or the equivalently innocuous char **object --> const char *const *object Nothing I can find in the FCD of the C standard forbids _any_ multi-level conversion---safe or unsafe. GCC, however, warns about every such conversion (even though it actually performs them). If it's going to complain, it really should only complain about unsafe conversions as per the C++ standard---despite the fact that all conversions appear to be legal in C. Am I wrong? Where does it state in the C standard that you cannot perform a multi-level qualifier promotion? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20230
