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Add a function to peek at the next character.

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This is necessary to correctly handle line continuations in a few places:
* Between an initial . and the subsequent digit in a floating constant
* Between the third and fourth characters of a %:%: digraph
* Between the second and third dots of a ... token

Previously, these would not be tokenized correctly, leading to spurious errors in the first and second cases above.

Here is a sample program illustrating the problem:

int printf(const char * restrict, ..\
\
??/
.);
int main(void) {
        double d = .??/
\
??/
\
1234;
        printf("%f\n", d);
}
This commit is contained in:
Stephen Heumann 2022-10-15 21:42:02 -05:00
parent 6fadd52fc2
commit 83ac0ecebf
2 changed files with 60 additions and 3 deletions
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61
Scanner.pas
View File

@ -4610,6 +4610,61 @@ else begin {record the name}
end; {CheckIdentifier}
function PeekCh: char;
{ Peek at the next character from the file, without advancing }
{ the character pointer. }
{ }
{ This is typically the character that will be produced by the }
{ next call to NextCh, but this function only deals with }
{ translation phases 1 and 2 (trigraphs and line continuations).}
{ It does not skip comments. }
label 1;
var
cp: ptr; {work pointer}
ch: char; {work character}
begin {PeekCh}
cp := chPtr;
1:
if cp = eofPtr then
PeekCh := chr(0)
else begin
ch := chr(cp^);
if ch = '?' then {handle trigraphs}
if ord4(eofPtr)-ord4(cp) > 2 then
if chr(ptr(ord4(cp)+1)^) = '?' then
if chr(ptr(ord4(cp)+2)^) in
['=','(','/',')','''','<','!','>','-'] then begin
case chr(ptr(ord4(cp)+2)^) of
'(': ch := '[';
'<': ch := '{';
'/': ch := '\';
'''': ch := '^';
'=': ch := '#';
')': ch := ']';
'>': ch := '}';
'!': ch := '|';
'-': ch := '~';
end; {case}
cp := pointer(ord4(cp)+2);
end; {if}
if ch = '\' then {handle line continuations}
if ord4(eofPtr)-ord4(cp) > 1 then
if charKinds[ptr(ord4(cp)+1)^] = ch_eol then begin
if ord4(eofPtr)-ord4(cp) > 2 then
if ptr(ord4(cp)+2)^ in [$06,$07] then
cp := pointer(ord4(cp)+1); {skip debugger characters}
cp := pointer(ord4(cp)+2);
goto 1;
end; {if}
PeekCh := ch;
end; {else}
end; {PeekCh}
procedure NextToken;
{ Read the next token from the file. }
@ -5180,7 +5235,7 @@ case charKinds[ord(ch)] of
else if ch = ':' then begin
NextCh;
token.isDigraph := true;
if (ch = '%') and (chPtr <> eofPtr) and (chr(chPtr^) = ':') then begin
if (ch = '%') and (PeekCh = ':') then begin
token.kind := poundpoundop; {%:%: digraph}
NextCh;
NextCh;
@ -5228,11 +5283,11 @@ case charKinds[ord(ch)] of
end;
ch_dot : begin {tokens that start with '.'}
if charKinds[chPtr^] = digit then
if charKinds[ord(PeekCh)] = digit then
DoNumber(false)
else begin
NextCh;
if (ch = '.') and (chPtr <> eofPtr) and (chr(chPtr^) = '.') then begin
if (ch = '.') and (PeekCh = '.') then begin
token.kind := dotdotdotsy;
NextCh;
NextCh;

2
cc.notes
View File

@ -1919,6 +1919,8 @@ int foo(int[42]);
212. If fgets() is called with an n value of 1, it should write a single terminating null character to the buffer. (It was writing two.)
213. If a floating-point constant beginning with . had a line continuation between the . and the first digit, a spurious error would be reported.
-- Bugs from C 2.1.0 that have been fixed -----------------------------------
1. In some situations, fread() reread the first 1K or so of the file.