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tccpp.c: Improve integer constant overflow warning

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Improve the warning about an integer constant overflow with the used
overflown value and the potentially aimed value.

This helps spotting the 0 to much in 0x80000000000000000.
This commit is contained in:
Stefan 2025-12-13 16:45:19 +01:00
parent fada98b1ce
commit 085bdf8997
1 changed files with 28 additions and 8 deletions
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36
tccpp.c
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@ -1995,7 +1995,7 @@ ST_FUNC void preprocess(int is_bof)
if (tok == '!' && is_bof) if (tok == '!' && is_bof)
/* '#!' is ignored at beginning to allow C scripts. */ /* '#!' is ignored at beginning to allow C scripts. */
goto ignore; goto ignore;
tcc_warning("Ignoring unknown preprocessing directive #%s", get_tok_str(tok, &tokc)); tcc_warning("ignoring unknown preprocessing directive #%s", get_tok_str(tok, &tokc));
ignore: ignore:
skip_to_eol(0); skip_to_eol(0);
goto the_end; goto the_end;
@ -2475,7 +2475,7 @@ static void parse_number(const char *p)
} }
} }
} else { } else {
unsigned long long n, n1; unsigned long long n = 0, n1 = 0;
int lcount, ucount, ov = 0; int lcount, ucount, ov = 0;
const char *p1; const char *p1;
@ -2486,7 +2486,6 @@ static void parse_number(const char *p)
b = 8; b = 8;
q++; q++;
} }
n = 0;
while(1) { while(1) {
t = *q++; t = *q++;
/* no need for checks except for base 10 / 8 errors */ /* no need for checks except for base 10 / 8 errors */
@ -2500,11 +2499,13 @@ static void parse_number(const char *p)
t = t - '0'; t = t - '0';
if (t >= b) if (t >= b)
tcc_error("invalid digit"); tcc_error("invalid digit");
n1 = n;
n = n * b + t; n = n * b + t;
/* detect overflow */ if (!ov)
if (n1 >= 0x1000000000000000ULL && n / b != n1) /* detect overflow */
ov = 1; if (n1 >= 0x1000000000000000ULL && n / b != n1)
ov = 1;
else
n1 = n;
} }
/* Determine the characteristics (unsigned and/or 64bit) the type of /* Determine the characteristics (unsigned and/or 64bit) the type of
@ -2554,7 +2555,26 @@ static void parse_number(const char *p)
} }
if (ov) if (ov)
tcc_warning("integer constant overflow"); /* Give a warning with values in case of an overflow. This helps to
spot the 0 too much in 0x8000'0000'0000'0000'0. It may even be
better to use a 0x8000'0000'0000'0000 from n1 instead of a 0 from
n after the overflow. This is at least undefined behavior.
The C99 to C23 standards state:
"Each constant shall have a type and the value of a constant
shall be in the range of representable values for its type."
"If an integer constant cannot be represented by any type ...,
then the integer constant has no type."
The C++ standards state:
"A program is ill-formed if one of its translation units contains
an integer-literal that cannot be represented by any of the
allowed types." */
tcc_warning(
b == 8
? "integer constant overflow, using %#llo; did you mean %#llo?"
: b == 10
? "integer constant overflow, using %llu, did you mean %llu?"
: "integer constant overflow, using %#llx; did you mean %#llx?",
n, n1);
tok = TOK_CINT; tok = TOK_CINT;
if (lcount) { if (lcount) {