Merge pull request #184 from xexyl/1991-dds

1991/dds/Makefile

@@ -62,7 +62,7 @@ CDEFINE=
 
 # Include files that are needed to compile
 #
-CINCLUDE=
+CINCLUDE= -include stdio.h
 
 # Optimization
 #
@@ -80,6 +80,7 @@ LIBS=
 #
 CC= cc
 
+CSILENCE= -Wno-implicit-function-declaration
 # Compiler add-ons or replacements for clang only
 #
 ifeq ($(CC),clang)
@@ -131,6 +132,9 @@ all: data ${TARGET}
 ${PROG}: ${PROG}.c
 	${CC} ${CFLAGS} $< -o $@ ${LIBS}
 
+a: a.c
+	${CC} ${CFLAGS} -Wno-return-type $< -o $@ ${LIBS}
+
 # alternative executable
 #
 alt: data ${ALT_TARGET}

1991/dds/README.md

@@ -14,7 +14,27 @@
 ### To run
 
 	./dds basic_program
-	./a.out
+	./a
+
+[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed some segfaults in
+this entry as well as making it so `a` (was `a.out`, see below) can be generated
+(as in the program did not work, at least with clang). The first segfault which
+was always triggered was due to the code `*q>' '&&(*q)--;`. This seems odd at
+first glance but it's pointing to `s` which was read-only memory as a `char *s`.
+It's now a `char s[]`. The second and third segfaults were caused if a file was
+not specified (or it the one specified did not exist or couldn't be opened for
+some reason) and if the output file could not be opened for writing. The
+allowing the generated code to compile with clang is something of a hack
+unfortunately. The code `return system(q-6);` ended up doing `return system("cc
+a.c");` but depending on the compiler this would trigger errors due to no
+function prototype specified and also a case where main() had a `return;`
+without any return value. Because the string `s` is complicated and because Cody
+did not want to inadvertently mess something up he changed that code to
+`system("make a");` and then added the right rule to the Makefile. Thus you now
+need both `make` and `cc`. If you use gcc you may change the system() call to
+what was given in this description to get a more authentic feel. If you do this
+you must then run `./a.out` not `./a`!  Thank you Cody for your assistance!
+
 
 ## Judges' comments
 
@@ -24,8 +44,8 @@ Make and run as follows:
 
 For example, the author suggests trying:
      
-	dds LANDER.BAS
+	./dds LANDER.BAS
-	a.out
+	./a
 
 Notice that a file a.c has been generated.  Can you tell how a.c was
 produced?  How does a.c relate to LANDER.BAS?

1991/dds/dds.c

@@ -1,7 +1,7 @@
 #include <stdio.h>
 #define Q r=R[*p++-'0'];while(
 #define B ;break;case
-char*s="Qjou!s\\311^-g\\311^-n\\311^-c\\::^-q-ma%mO1JBHm%BQ-aP1J[O1HB%[Q<nbj\
+char s[]="Qjou!s\\311^-g\\311^-n\\311^-c\\::^-q-ma%mO1JBHm%BQ-aP1J[O1HB%[Q<nbj\
 o)*|gps)<<*txjudi)m*|aQdbtf!::::;sfuvso<aQefgbvmu;aQ<m,,a%CQ<csfbla%bQ<aN2!Q\
 \ndbtf!aP2Q;m>aP2Q<a%!D12J!JGJHJOJQJFJSJJJMHS%HD12D12N3!N4\nJUJT%UQm>aP4HC%T\
 Qs\\q,,^>m,2<m>aP4HC%SD12N1\nJNQm>s\\..q^aHC%NHb%GN1!D32P3%RN1UP1D12JPQUaP1H\
@@ -10,8 +10,8 @@ R%PN4\nQ<g\\(aP3Q(^>aP2Q,2<n\\(aP3Q(^>aP4Hb%OD12D12N2!N3\nJVP3Q,,<jg)aP3Q=>n\
 aP1Q*aHb%FN1\nQm>::::aHC%VP3Q>bupj)hfut)c**aHb%JD12JON1!Qjg)a%LN1UP1D12JIQUa\
 P1HL%IQ*m>aN2!N2\nP2Q<fmtf!m,,aHC%MN1!N2>P2Q>aN2\nP2Hbdd!b/d";int k;char R[4][99]
 ;main(c,v)char**v;{char*p,*r,*q;for(q=s;*q;q++)*q>' '&&(*q)--;{FILE*i=fopen(v
-[1],"r"),*o=fopen(q-3,"w");for(p=s;;p++)switch(*p++){B'M':Q(k=fgetc(i))!=EOF
+[1],"r"),*o=fopen(q-3,"w");if(!i||!o)return 1;for(p=s;;p++)switch(*p++){B'M':
-&&k!=*p)*r++=k;if(k==EOF){fputs("}}\n",o);fclose(o);return system(q-6);}*r=0
+Q(k=fgetc(i))!=EOF&&k!=*p)*r++=k;if(k==EOF){fputs("}}\n",o);fclose(o);return
-B'P':while(*p!='`')fputc(*p++,o)B'O':Q*r)fputc(*r++,o);p--B'C':k=0;Q k<*p-'0'
+system("make a");}*r=0 B'P':while(*p!='`')fputc(*p++,o)B'O':Q*r)fputc(*r++,o);
-)(*r++=fgetc(i),k++);*r=0 B'I':k= *p;if(**R==k)goto G B'G':k= *p;G:p=s;while(
+p--B'C':k=0;Q k<*p-'0')(*r++=fgetc(i),k++);*r=0 B'I':k= *p;if(**R==k)goto G
-*p!='$'||p[1]!= k)p++;p++B'N':R[*p-'0'][0]++;}}}
+B'G':k= *p;G:p=s;while(*p!='$'||p[1]!= k)p++;p++B'N':R[*p-'0'][0]++;}}}