diff --git a/1994/shapiro/README.md b/1994/shapiro/README.md index 942f8f9df..cd4e67338 100644 --- a/1994/shapiro/README.md +++ b/1994/shapiro/README.md @@ -10,17 +10,21 @@ USA make all -[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) pointed out a potential -bug on systems where `EOF != -1`. The problem is that `getc()` and the related -functions do not return `-1` on EOF or error but rather `EOF` but the program -assumes `-1` (conversely when using the `getopt()` functions one should not -check for EOF but -1 as the functions return -1 not EOF but the standard does -not require `EOF` to be -1, just a negative number. However changing it to check -for `!=EOF` caused a problem due to the clever encoding of the code. See -[bugs.md](/bugs.md) for more details if you wish to try and fix this (Cody is -here and there working on it along with other things and will change this -message when it's fixed assuming it's feasible). - +[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed a bug on systems +where `EOF != -1`. The problem is that `getc()` and the related functions do not +return `-1` on EOF or error but rather `EOF`. However `EOF` is not required to be +`-1` but merely an int < 0 and this program assumed that `getc()` will return +`-1` on EOF or error, not `EOF`. On systems where `EOF != -1` it could be a +problem. For the same reason one should not use `EOF` for the `getopt()` +functions as they return `-1` when all options are parsed (for details on the +definition of `EOF` see `7.21 Input/output` subsection 1 of the +standard). An interesting problem occurred where changing the `-1` to `EOF` +caused both `warning: illegal character encoding in string literal` and `error: +source file is not valid UTF-8`. But since `EOF` is simply an int < 0 and making +the loop condition check that the return value is >= 0 does not cause a +compilation error and it functions correctly it will address the systems where +`EOF != -1` just as if it checked for `!= EOF`. Thank you Cody for your +assistance! ## To run: diff --git a/1994/shapiro/shapiro.c b/1994/shapiro/shapiro.c index d2da120c7..9a1548dcc 100644 --- a/1994/shapiro/shapiro.c +++ b/1994/shapiro/shapiro.c @@ -11,7 +11,7 @@ /*T*/,"r");for (;( L/*KPUOWOWMUQ LLOLMPULWLWL WLW LWLWLWLWLWLW LWLWLULVOXP LLV LLLOLMPULOL - MMNP*/=getc (J) )!= -1;L/* + MMNP*/=getc (J) )>= 0;L/* OLWLRMMQUL VOX PLLVLLLMQO PMPYPXPNP MQL LVLLLWPSP XPOQNQOPMQ LLV LTj*/>='J' diff --git a/1994/shapiro/shapiro.md b/1994/shapiro/shapiro.md index 28b3e4eca..071ee2296 100644 --- a/1994/shapiro/shapiro.md +++ b/1994/shapiro/shapiro.md @@ -13,7 +13,7 @@ This is a very simple program: 5. FILE *J; 6. J=fopen(__FILE__,"r"); 7. for(; - 8. (L=getc(J))!=EOF; + 8. (L=getc(J))>=0; 9. L>='J'&&L<='J'+15 && 10. ((M=!M)?K=L:putchar(K-'J'|(L-'J'<<4))) 11. ); diff --git a/bugs.md b/bugs.md index 2a98c56c7..4fdfd2019 100644 --- a/bugs.md +++ b/bugs.md @@ -572,82 +572,6 @@ or was killed. See the README.md for more details. If you don't feel comfortable changing it to `EOF` Cody will happily do it for you but otherwise go right ahead. We'll credit you in the README.md file regardless. - -## STATUS: doesn't work with some platforms - please help us fix - -[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) pointed out a potential -bug in [1994/shapiro](1994/shapiro/shapiro.c) on systems where `EOF != -1` as -the code assumes that `EOF` will always be `-1`. As the standard says (see `7.21 -Input/output` subsection 1) it only has to be a negative int, not -necessarily `-1`. The problem is that the source file's last character is a -newline (10 in decimal) and so on systems where `EOF != -1` the `getc()` -functions would not terminate the loop (but see below). This would cause a -breakage in the entry. - -However due to clever encoding of the code it is not a simple matter of applying -the following patch: - -```diff -diff --git i/1994/shapiro/shapiro.c w/1994/shapiro/shapiro.c -index d2da120c7bc4e251b7624859e48f47f188d398e9..e054a1ceb067b82bf37c07e5ce75e82be7a03b85 100644 ---- i/1994/shapiro/shapiro.c -+++ w/1994/shapiro/shapiro.c -@@ -9,11 +9,11 @@ - /*PPPPVPOQMQRPR*/=0;FILE/*TPSLUMWQT*/ * - J/*MPRPKPLQ*/; J= fopen(__FILE__ - /*T*/,"r");for (;( L/*KPUOWOWMUQ - LLOLMPULWLWL WLW LWLWLWLWLWLW - LWLWLULVOXP LLV LLLOLMPULOL -- MMNP*/=getc (J) )!= -1;L/* -+ MMNP*/=getc (J) )!=EOF;L/* - OLWLRMMQUL VOX PLLVLLLMQO - PMPYPXPNP MQL LVLLLWPSP - XPOQNQOPMQ LLV LTj*/>='J' - &&L/*LRPYP OQL QMQLLVLLL - OLMQVOXPL LVL LLVOe*/<= - -``` - -as doing so will cause `warning: illegal character encoding in string -literal` and the error `error: source file is not valid UTF-8`. Looking at the -file you'll see on line 4 of `shapiro_t2.c`: - - -``` -char *a[]={"%c+------------+\n","%c+%3dPRÒ<82>3·Âå&Â"2W6öæF6'Â"Ò<96>æVGW6'¢ <82>öV'7'Â"R2Çå&Â"Â^E33sÃ^E33³UB¶cS³<83>T2Ç^E33<83>#Ò·£<90>æF^G"¶ÕÕ³^GÃ^BÃ^RsÃ^RCÃ^R^SÃ^BÓ·£Ð^V<96>æ<86>bÇ2<96><92>æF^Gb·3<86>^V&^G¢¢^B2¶£°7<86>^V&^GB¶E^CÓÅ¢RÆbÖc³£@<97>ÖVöE^Gr¶£`<94>ÄT^D¢<82>Æ¢<92>¶£p<87><96>ÆV^F<82>ÒÒb^Fbb^B^R^B<97>^FW<86>B<96>^Bbb^B^Rbö&·<86><92><92>²£<80>ÖcFö^FWæ<86>bÓbÆÃ^SÃ"^R&<92>²<93>ÖcFö^FWæ<86><82>bÓbÆÃ^S<93>²^RÃ""'<92>²£`ö&<87>²³<93>²<97>f<86>b<96>²gvVF7<87>BÆB^CÃ<92><96>²C¶5G'ÇVæ<86>B<96>Ò^RÓÕsÂ^Es²£<90>f<86>¢BÖÓs^Bs²b<96>²7^G'<97>æFg<86>¢2Æ"R2Çå&ÂB¶^R<93>²ó<86>2GGöVGÇbÃbÓbÆB¶^RÃ^B<93>Ò§<90>f<86>¢Bæs^Bs²b<96>ò<86><82>ÆRÃBÆ^BÃ^B<93>ÒWÆ6W¶G<97>ÖV<86>br<96>²SÖ^S67F<97>ÖV<86>Âö6^VÆF<97>ÖV<86>br<96><92>²£`ö&<87>b×^S³cÇc³c·²<92>ò<86><82>Æb^WÒ^Scbb^WÒcÓ^RÃb·r^BsÂ^RF÷<96><86>R¶"¶e×<95>Âb<97>2ÇVV^F<87>^R<93>²Ó×ק  -``` - -when it should be something entirely different. For what it should be try -running `make clobber all ; cat shapiro_t2.c` or else look at the second program -in the spoilers file [shapiro.md](1994/shapiro/shapiro.md]). - -Cody is working will be working on this here and there but if you have a fix or -any suggestions you're welcome to provide it or them. - -Cody points you to the README.md file for what should happen when the entry is -successfully compiled (including no compilation errors when running `make -clobber all`). - -Another problem is that in the [shapiro.md](shapiro.md) file the first program -does not work. - -### Tips on this entry: - -Cody provides some tips on this entry: - -First: the comments are the important part of this entry. Remove them and the -program breaks. - -Second and perhaps part of the problem with changing the code to `EOF` instead -of `-1` is the `for` loop particularly to do with the bitwise operations, -perhaps also made worse by the seemingly gibberish comments. - -Another important point is that the Makefile compiles the program as -`shapiro_t1` so that the source code that corresponds with it is actually -[shapiro.c](1994/shapiro/shapiro.c). But notice how running `shapiro_t1` results -in different functionality than `shapiro` itself? The source code that -`shapiro_t1` generates, `shapiro_t2.c`, is what is compiled into `shapiro`. - # 1995