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The switch/case operation was entirely performed on int64_t, resulting
in a warning and bad code to be emitted on 64 bit machines when used on
an unsigned long with a case range whose signed representation starts
positive and ends negative like in the example below:
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
int nbdg(unsigned long n)
{
switch (n) {
case 1UL ... 9UL: return 1;
case 10UL ... 99UL: return 2;
case 100UL ... 999UL: return 3;
case 1000UL ... 9999UL: return 4;
case 10000UL ... 99999UL: return 5;
case 100000UL ... 999999UL: return 6;
case 1000000UL ... 9999999UL: return 7;
case 10000000UL ... 99999999UL: return 8;
case 100000000UL ... 999999999UL: return 9;
case 1000000000UL ... 9999999999UL: return 10;
case 10000000000UL ... 99999999999UL: return 11;
case 100000000000UL ... 999999999999UL: return 12;
case 1000000000000UL ... 9999999999999UL: return 13;
case 10000000000000UL ... 99999999999999UL: return 14;
case 100000000000000UL ... 999999999999999UL: return 15;
case 1000000000000000UL ... 9999999999999999UL: return 16;
case 10000000000000000UL ... 99999999999999999UL: return 17;
case 100000000000000000UL ... 999999999999999999UL: return 18;
case 1000000000000000000UL ... 9999999999999999999UL: return 19; // this one
case 10000000000000000000UL ... ULONG_MAX: return 20;
}
return 0;
}
int main(int argc, char **argv)
{
unsigned long v = strtoul(argc > 1 ? argv[1] : "1111", NULL, 0);
printf("%lu : %d\n", v, nbdg(v));
return 0;
}
$ tcc dg.c
dg.c:26: warning: empty case range
$ x="";for i in 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0; do x=$x$i; ./a.out $x;done
1 : 1
12 : 2
123 : 3
1234 : 4
12345 : 5
123456 : 6
1234567 : 7
12345678 : 8
123456789 : 9
1234567890 : 10
12345678901 : 11
123456789012 : 12
1234567890123 : 13
12345678901234 : 14
123456789012345 : 15
1234567890123456 : 16
12345678901234567 : 17
123456789012345678 : 18
1234567890123456789 : 0
12345678901234567890 : 20
What this patch does is to use a separate set of signed and unsigned
case_cmp functions depending on whether the expression is signed or
unsigned, and also does this to decide when to emit the warning.
The bad code on output was caused by the removal of the unsigned bit
resulting from the signed sort, which causes only signed comparisons
to be emitted in the asm code. As such some sets could not match.
Note that there is no way to rely on the values only to sort properly
nor to emit the warning because we're effectively dealing with 65-bit
arithmetic here and any two values will have a different behavior
depending on the signed or unsigned expectation.
For unsigned expressions now the warning only happens when bounds are
switched, For signed expressions (e.g. if the input is signed long
above), the warning remains and the abnormal output as well. In both
cases this remains consistent with what gcc produces.
Tiny C Compiler - C Scripting Everywhere - The Smallest ANSI C compiler ----------------------------------------------------------------------- Features: -------- - SMALL! You can compile and execute C code everywhere, for example on rescue disks. - FAST! tcc generates optimized x86 code. No byte code overhead. Compile, assemble and link about 7 times faster than 'gcc -O0'. - UNLIMITED! Any C dynamic library can be used directly. TCC is heading toward full ISOC99 compliance. TCC can of course compile itself. - SAFE! tcc includes an optional memory and bound checker. Bound checked code can be mixed freely with standard code. - Compile and execute C source directly. No linking or assembly necessary. Full C preprocessor included. - C script supported : just add '#!/usr/local/bin/tcc -run' at the first line of your C source, and execute it directly from the command line. Documentation: ------------- 1) Installation on a i386/x86_64/arm Linux/OSX/FreeBSD host ./configure make make test make install Notes: For OSX and FreeBSD, gmake should be used instead of make. For Windows read tcc-win32.txt. makeinfo must be installed to compile the doc. By default, tcc is installed in /usr/local/bin. ./configure --help shows configuration options. 2) Introduction We assume here that you know ANSI C. Look at the example ex1.c to know what the programs look like. The include file <tcclib.h> can be used if you want a small basic libc include support (especially useful for floppy disks). Of course, you can also use standard headers, although they are slower to compile. You can begin your C script with '#!/usr/local/bin/tcc -run' on the first line and set its execute bits (chmod a+x your_script). Then, you can launch the C code as a shell or perl script :-) The command line arguments are put in 'argc' and 'argv' of the main functions, as in ANSI C. 3) Examples ex1.c: simplest example (hello world). Can also be launched directly as a script: './ex1.c'. ex2.c: more complicated example: find a number with the four operations given a list of numbers (benchmark). ex3.c: compute fibonacci numbers (benchmark). ex4.c: more complicated: X11 program. Very complicated test in fact because standard headers are being used ! As for ex1.c, can also be launched directly as a script: './ex4.c'. ex5.c: 'hello world' with standard glibc headers. tcc.c: TCC can of course compile itself. Used to check the code generator. tcctest.c: auto test for TCC which tests many subtle possible bugs. Used when doing 'make test'. 4) Full Documentation Please read tcc-doc.html to have all the features of TCC. Additional information is available for the Windows port in tcc-win32.txt. License: ------- TCC is distributed under the GNU Lesser General Public License (see COPYING file). Fabrice Bellard.