d38dc2c833
A '//' comment after a #define body was captured INTO the stored macro body. Expansion buffers carry no newline to end it, so when the macro expanded inside a spliced line (a function-like macro's substituted body, as in the report's MIN(credits, m[e][CREDITS])), the '//' ate the rest of the splice and the parse failed with a baffling 'unexpected ;' attributed to the outer macro. The same missed strip made '#undef X // why' erase nothing and '#ifdef X // why' look up the wrong name and silently take the false branch. Comments are whitespace (C translation phase 3). dispatch_directive now strips them from the payload before parsing for #define (name, params, body -- body also right-trimmed so a stripped comment can't turn '1' vs '1 ' into a spurious redefinition warning), #undef, #ifdef, #ifndef, and #pragma (word-list payload); #if/#elif already stripped. strip_directive_comments() now folds a block comment to ONE space instead of nothing, so '1 -/*c*/-1' keeps its token boundaries instead of pasting '--'. #error/#warn/#echo payloads stay raw. Covered by five new Preprocessor unit tests (the report's repro shape, paste-prevention via #if branch selection, param-list comment, testsuite/single/tests/compiler/preprocessor.lpc; documented in docs/lpc/preprocessor/define.md. Fixes #1240 Claude-Session: https://claude.ai/code/session_016FMBJLkpkpVpZdz6PWzeWe Co-authored-by: Claude <noreply@anthropic.com>
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| title |
|---|
| preprocessor / define |
#define and #undef
#define creates a macro: a name that is replaced by a body of
text wherever it appears later in the file.
Object-like macros
#define MAX_HP 100
#define GREETING "Welcome to " MUD_NAME
Every later occurrence of the name (as a whole identifier — not inside strings, comments, or longer identifiers) is replaced by the body.
Function-like macros
A parameter list attached directly to the name (no space before
() makes the macro function-like:
#define SQUARE(x) ((x) * (x))
#define MSG(who, text) tell_object(who, text "\n")
Arguments are collected with full nesting awareness — commas inside parentheses, strings, or character literals do not split arguments. Parenthesize parameters in the body (as above) to avoid precedence surprises at the use site.
Inside a macro body, #param produces the argument's text as a string
literal, and a ## b pastes two tokens together. ## may not appear
at the very start or end of a body.
Expansion and rescan
A macro's body is rescanned after substitution, so macros may reference other macros freely. A macro that (directly or indirectly) references itself stops expanding at the self-reference instead of recursing forever, as in C.
Because #if expressions are evaluated over the same token stream,
arithmetic keeps C precedence across macro boundaries:
#define X 1+1
#if X*2 == 3 // 1+1*2 -- true
Multi-line macros
End a line with \ to continue the definition:
#define LONG_MACRO(x) do { \
write(x); \
} while (0)
A block comment opened on a directive line may also span lines — it
reads as whitespace and does not end the directive, so both of these
define WARNING_LEVEL as 1:
#define WARNING_LEVEL 1 /* change to a higher value to
show more warnings */
#define WARNING_LEVEL 1 // single-line form
Text after the comment's close on its final line still belongs to the directive, matching C.
Comments on a directive line are whitespace, never part of the macro:
a trailing // or /* */ after the body (or after the name on
#undef/#ifdef) is stripped before the directive is parsed, and a
block comment inside the body separates tokens like a space would:
#define CREDITS "credits" // key into the economy mapping
Redefinition
Redefining a macro with a different body is allowed: the compiler
emits a warning (with a note pointing at the previous definition) and
the new definition takes effect. Redefining with an identical body is
silent. Redefining or #undef-ing a predefined macro (__FILE__,
FLUFFOS, ...) is a compile error.
#undef
#undef MAX_HP
Removes a user macro definition; the name is ordinary text again.
#undef of an unknown name is harmless.