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Recognise and obey `line directives in the preprocessor (issue #488) 

To correctly restore the file name and line number after including a
file or expanding a macro, the preprocessor needs to be aware of the
changes introduced by `line directives. The `line directive still
needs to be passed on to the main compiler so it can track the
changes too.

To avoid duplicate error messages, the preprocessor silently ignores
invalid `line directives, relying on the main compiler to report the
errors.
This commit is contained in:
Martin Whitaker 2021-03-13 23:38:30 +00:00
parent 45db0db8b3
commit 9a2c43ec34
1 changed files with 91 additions and 1 deletions
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92
ivlpp/lexor.lex
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@ -33,6 +33,8 @@
static void output_init(void);
#define YY_USER_INIT output_init()
static void handle_line_directive(void);
static void def_start(void);
static void def_add_arg(void);
static void def_finish(void);
@ -215,10 +217,17 @@ W [ \t\b\f]+
* older versions of flex (at least 2.5.31); they are supposed to
* be implied, according to the flex manual.
*/
keywords (include|define|undef|ifdef|ifndef|else|elsif|endif)
keywords (line|include|define|undef|ifdef|ifndef|else|elsif|endif)
%%
/* Recognize and handle the `line directive. Also pass it through to
* the output so the main compiler is aware of the change.
*/
^[ \t]?"`line"[ \t]+.+ { handle_line_directive(); ECHO; }
/* Detect single line comments, passing them directly to the output.
*/
"//"[^\r\n]* { ECHO; }
/* detect multiline, c-style comments, passing them directly to the
@ -693,6 +702,87 @@ keywords (include|define|undef|ifdef|ifndef|else|elsif|endif)
<<EOF>> { if (!load_next_input()) yyterminate(); }
%%
/*
* Parse a `line directive and set the current file name and line
* number accordingly. This ensures we restore the correct name
* and line number when returning from an include file or macro
* expansion. Ignore an invalid directive - the main compiler
* will report the error.
*/
static void handle_line_directive(void)
{
char *cp;
char *cpr;
unsigned long lineno;
char*fn_start;
char*fn_end;
/* Skip any leading space. */
cp = strchr(yytext, '`');
/* Skip the `line directive. */
assert(strncmp(cp, "`line", 5) == 0);
cp += 5;
/* strtoul skips leading space. */
lineno = strtoul(cp, &cpr, 10);
if (cp == cpr || lineno == 0) {
return;
}
cp = cpr;
/* Skip the space between the line number and the file name. */
cpr += strspn(cp, " \t");
if (cp == cpr) {
return;
}
cp = cpr;
/* Find the starting " and skip it. */
fn_start = strchr(cp, '"');
if (cp != fn_start) {
return;
}
fn_start += 1;
/* Find the last ". */
fn_end = strrchr(fn_start, '"');
if (!fn_end) {
return;
}
/* Skip the space after the file name. */
cp = fn_end + 1;
cpr = cp;
cpr += strspn(cp, " \t");
if (cp == cpr) {
return;
}
cp = cpr;
/* Check that the level is correct, we do not need the level. */
if (strspn(cp, "012") != 1) {
return;
}
cp += 1;
/* Verify that only space is left. */
cp += strspn(cp, " \t");
if ((size_t)(cp-yytext) != strlen(yytext)) {
return;
}
/* Update the current file name and line number. Subtract 1 from
the line number because `line sets the number for the next
line, and 1 because our line numbers are zero-based. This
will underflow on line 1, but that's OK because we are using
unsigned arithmetic. */
assert(istack);
realloc(istack->path, fn_end-fn_start+1);
strncpy(istack->path, fn_start, fn_end-fn_start);
istack->path[fn_end-fn_start] = '\0';
istack->lineno = lineno - 2;
}
/* Defined macros are kept in this table for convenient lookup. As
* `define directives are matched (and the do_define() function
* called) the tree is built up to match names with values. If a