This is a partial list of how `gcc -traditional' disagrees with traditional C compilers (perhaps only some of them). Most of these differences are not bugs. --------------------------------------------------------------------------- K&R-1 (2.4.3) says: "If the character following a backslash is not one of those specified {in the table above}, the backslash is ignored." Up until recently, `gcc -traditional' complained about \x \a and \v appearing in a character or string literal. I believe however that this non-feature has been eliminated (recently). --------------------------------------------------------------------------- When in -traditional mode, gcc allows the following erroneous pair of declarations to appear together in a given scope: typedef int foo; typedef foo foo; --------------------------------------------------------------------------- K&R-1 (8.5) says: "No field may be wider than a word." Gcc however allows: struct S { int i:33; }; --------------------------------------------------------------------------- In K&R-1 there is no restriction against comments crossing include file boundaries. Gcc however doesn't allow this, even when in -traditional mode. --------------------------------------------------------------------------- Regarding the length of identifiers, K&R-1 (2.2) says: "No more than the first eight characters are significant, although more may be used." Gcc treats all characters of identifiers as significant, even when in -traditional mode. --------------------------------------------------------------------------- K&R-1 (2.2) says: "An identifier is a sequence of letters and digits; the first character must be a letter. The underscore _ counts as a letter." Gcc also allows dollar signs in identifiers. (This may also be an issue for the -pedantic option.) ---------------------------------------------------------------------------