\fontscheme default \graphics default \paperfontsize default \spacing single \papersize Default \paperpackage a4 \use_geometry 0 \use_amsmath 0 \paperorientation portrait \secnumdepth 3 \tocdepth 3 \paragraph_separation indent \defskip medskip \quotes_language english \quotes_times 2 \papercolumns 1 \papersides 1 \paperpagestyle default \layout Title LyX and Literate Programming \newline An example program \layout Author Edmar Wienskoski Jr. \newline edmar-w-jr@technologist.com \layout Date \latex latex \backslash today \layout Standard \begin_inset LatexCommand \tableofcontents \end_inset \layout Section Introduction \layout Standard After typesetting a document, LyX scans the LaTeX log file looking for errors. For each error found, the line number is obtained and a error box is displayed in the LyX screen at that position. \layout Standard To use this feature to view compilation errors while working with literate documents, we need a program that filters the compilation errors and puts them in a format suitable for LyX reading it. \layout Standard In this document we present a filter that recognizes compilation error messages from noweb, gnu C, and the IBM C compiler (xlc). \layout Standard The filter is required to read from standard input, parse for error messages and copy the error messages to the standard output. During the output process, the filter must present the error messages in a format that LyX can interpret, currently, the LaTeX error message format. Of course, nothing will prevent future LyX releases from being able to read other formats as well (like gcc error messages for example). This mechanism is necessary to fully explore the literate programming tool’s capabilities. \layout Section Algorithm \layout Scrap <<Function bodies>>= \newline \newline main (int argc, char **argv) \newline \newline \protected_separator if (argc == 2) { \newline \protected_separator \protected_separator \protected_separator switch (argv[1][0]) { \newline \protected_separator \protected_separator \protected_separator case ’n’: \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator <<Scan input for noweb error messages>> \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator case ’x’: \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator <<Scan input for xlc error messages>> \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator case ’a’: \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator <<AIX system using both noweb and xlc>> \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator case ’s’: \newline \protected_separator \protected_separator \protected_separator case ’b’: \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator <<Solaris and Linux systems using both noweb and gcc>> \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator case ’g’: \newline \protected_separator \protected_separator \protected_separator default: \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator <<Scan input for gcc error messages>> \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator \newline \protected_separator else { \newline \protected_separator \protected_separator \protected_separator <<Scan input for gcc error messages>> \newline \protected_separator \newline \newline \layout Scrap <<Function prototypes>>= \newline int main (int argc, char **argv); \newline \layout Section Data Structures \layout Standard We resort to some global variables to allow access from several different routines. These are the buffer and related pointers used during the parse of the input. \layout Scrap <<Global variables>>= \newline \protected_separator \protected_separator \protected_separator buffer[200][200]; \newline \protected_separator \protected_separator \protected_separator \protected_separator last_buf_line; \newline \protected_separator \protected_separator \protected_separator \protected_separator last_err_line; \newline \protected_separator \protected_separator \protected_separator \protected_separator err_line; \newline \layout Section The output format \layout Standard The output format mimics the LaTeX error messages format. This function prints a number of lines residing in the global variable \family typewriter buffer \family default , a program name and line number. There is no special requirement on the input strings, they can be anything. \layout Scrap <<Function bodies>>= \newline \newline output_error (int buf_size, int error_line, char *tool) \newline \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \newline \protected_separator \newline \protected_separator fprintf(stdout, "! Build Error: ==> %s ==> \backslash n", tool); \newline \protected_separator for (i=0; i<buf_size; i++) \newline \protected_separator \protected_separator \protected_separator fprintf(stdout, "%s", buffer[i]); \newline \protected_separator fprintf(stdout, " ... \backslash \backslash nl.%d ... \backslash \backslash n", error_line); \newline \newline \layout Scrap <<Function prototypes>>= \newline void output_error (int buf_size, int error_line, char *tool); \newline \layout Section Functions Implementation \layout Standard Both noweave and notangle routines, always output one single line for each error found, thus to scan the buffer for noweb error messages is enough to exam one input line at a time. Note that the noweb software does not provide a line error number, so all errors boxes related to noweb messages will be displayed at the beginning of the file. \layout Scrap <<Scan input for noweb error messages>>= \newline \newline \protected_separator last_buf_line = 0; \newline \protected_separator while (fgets(buffer[0], 200, stdin)) { \newline \protected_separator \protected_separator \protected_separator if (noweb_try(0)) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator output_error(1, 0, "noweb"); \newline \protected_separator \newline \newline \layout Standard The examination itself is very inefficient. Unfortunately noweb doesn’t have any characteristic that would help to identify one of its error messages. The solution is to collect all possible output messages in an array of strings, and turn the examination process into a linear search in this array. \layout Scrap <<Global variables>>= \newline char *noweb_msgs[] = { \newline \protected_separator "couldn’t open file", \newline \protected_separator "couldn’t open temporary file", \newline \protected_separator "error writing temporary file", \newline \protected_separator "ill-formed option", \newline \protected_separator "unknown option", \newline \protected_separator "Bad format sequence", \newline \protected_separator "Can’t open output file", \newline \protected_separator "Can’t open temporary file", \newline \protected_separator "Capacity exceeded:", \newline \protected_separator "Ignoring unknown option -", \newline \protected_separator "This can’t happen:", \newline \protected_separator "non-numeric line number in" \newline \newline \layout Standard A noweb error message can be any string that contains a matching pair of \protected_separator \protected_separator \protected_separator > >, or any of the above strings. \layout Scrap <<Function bodies>>= \newline \newline noweb_try (int buf_line) \newline \newline \protected_separator char \protected_separator \protected_separator \protected_separator *s, *b; \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \newline \protected_separator \newline \protected_separator b = buffer[buf_line]; \newline \protected_separator s = strstr(b, "<<"); \newline \protected_separator if (s != NULL) { \newline \protected_separator \protected_separator \protected_separator s = strstr(s+2, ">>"); \newline \protected_separator \protected_separator \protected_separator if (s != NULL) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator return 1; \newline \protected_separator else { \newline \protected_separator \protected_separator \protected_separator for (i=0; i<12; i++) { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator s = strstr (b, noweb_msgs[i]); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator if (s != NULL) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator \newline \protected_separator \protected_separator \protected_separator if (s != NULL) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator return 1; \newline \protected_separator \newline \protected_separator return 0; \newline \newline \layout Scrap <<Function prototypes>>= \newline int noweb_try (int buf_line); \newline \layout Standard The xlc compiler always outputs one single line for each error found, thus to scan the buffer for xlc error messages it is enough to exam one input line at a time. \layout Scrap <<Scan input for xlc error messages>>= \protected_separator \newline \newline \protected_separator last_buf_line = 0; \newline \protected_separator while (fgets(buffer[last_buf_line], 200, stdin)) { \newline \protected_separator \protected_separator \protected_separator if (xlc_try(0)) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator output_error(1, err_line, "xlc"); \newline \protected_separator \newline \newline \layout Standard A xlc error message is easy to identify. Every error message starts with a quoted string with no spaces, a comma, a space, the word \begin_inset Quotes eld \end_inset \begin_inset Quotes erd \end_inset , a space, and some variable text. The following routine tests if a given buffer line matches this criteria: \layout Scrap <<Function bodies>>= \newline \newline xlc_try (int buf_line) \newline \newline \protected_separator char \protected_separator \protected_separator \protected_separator *s, *t; \newline \protected_separator \newline \protected_separator t = buffer[buf_line]; \newline \protected_separator s = t+1; \newline \protected_separator while (*s != ’"’ && *s != ’ ’ && *s != ’ \backslash \newline \protected_separator \protected_separator \protected_separator s++; \newline \protected_separator if (*t != ’"’ || *s != ’"’ || strncmp(s+1, ", line ", 7) != 0) \newline \protected_separator \protected_separator \protected_separator return 0; \newline \protected_separator s += 8; \newline \protected_separator err_line = atoi(s); \newline \protected_separator return 1; \newline \newline \layout Scrap <<Function prototypes>>= \newline int xlc_try (int buf_line); \newline \layout Standard The gcc compiler error messages are more complicated to scan. Each error can span more than one line in the buffer. The good news is that every buffer line on each error has the same pattern, and share the same line number. Thus the strategy will be to accumulate lines in the buffer while the reported line number is still the same. At the time they differ, all the accumulated lines, except the last one, will belong to one single error message, which now can be output-ed to LyX. \layout Standard Every gcc error message contains a string with no space followed by a \begin_inset Quotes eld \end_inset \begin_inset Quotes eld \end_inset If the next character is a space, then this line is a header of a error message and the next line will detail the line number of the source code where the error was found. Otherwise, the next thing is a integer number followed by another \begin_inset Quotes eld \end_inset \begin_inset Quotes eld \end_inset \layout Scrap <<Scan input for gcc error messages>>= \newline \newline \protected_separator char \protected_separator \protected_separator \protected_separator *s, *t; \newline \protected_separator \newline \protected_separator last_buf_line = 0; \newline \protected_separator while (fgets(buffer[last_buf_line], 200, stdin)) { \newline \protected_separator \protected_separator \protected_separator /****** Skip lines until I find an error */ \newline \protected_separator \protected_separator \protected_separator s = strpbrk(buffer[last_buf_line], " :"); \newline \protected_separator \protected_separator \protected_separator if (s == NULL || *s == ’ ’) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator continue; /* No gcc error found here */ \newline \protected_separator \protected_separator \protected_separator do { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator <<gcc error message criteria is to find a "...:999:" or a "...: ">> \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator /****** OK It is an error message, get line number */ \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator err_line = atoi(s+1); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator if (last_err_line == 0 || last_err_line == err_line) { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator last_err_line = err_line; \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator continue; /* It’s either a header or a continuation, don’t output yet */ \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \newline \protected_separator \protected_separator \protected_separator /****** Completed the scan of one error message, output it to LyX */ \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator discharge_buffer(1); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator while (fgets(buffer[last_buf_line], 200, stdin)); \newline \protected_separator \newline \protected_separator \protected_separator /****** EOF completes the scan of whatever was being scanned */ \newline \protected_separator discharge_buffer(0); \newline \newline \layout Scrap <<gcc error message criteria is to find a "...:999:" or a "...: ">>= \newline /****** Search first ":" in the error number */ \newline s = strpbrk(buffer[last_buf_line], " :"); \newline last_buf_line++; \newline if (s == NULL || *s == ’ ’) \newline \protected_separator <<No gcc error found here, but it might terminate the scanning of a previous one>> \newline /****** Search second ":" in the error number */ \newline t = strpbrk(s+1, " :"); \newline if (t == NULL || *t == ’ ’) \newline \protected_separator <<No gcc error found here, but it might terminate the scanning of a previous one>> \newline /****** Verify if is all digits between ":" */ \newline if (t != s+1+strspn(s+1, "0123456789")) \newline \protected_separator <<No gcc error found here, but it might terminate the scanning of a previous one>> \newline \layout Scrap <<No gcc error found here, but it might terminate the scanning of a previous one>>= \newline \newline \protected_separator \protected_separator err_line = 0; \newline \protected_separator \protected_separator discharge_buffer(1); \newline \protected_separator \protected_separator continue; \newline \newline \layout Standard As we mentioned, when the scan of one gcc error message is completed everything in the buffer except the last line is one single error message. But if the scan terminates with a EOF or through finding one line that does not match the gcc error message criteria, then there is no \begin_inset Quotes eld \end_inset last line \begin_inset Quotes erd \end_inset in the buffer to be concerned with. In those cases we empty the buffer completely. \layout Scrap <<Function bodies>>= \newline \newline discharge_buffer (int save_last) \newline \newline \protected_separator if (last_err_line != 0) { \newline \protected_separator \protected_separator \protected_separator if (save_last != 0) { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator output_error(last_buf_line-1, last_err_line, "gcc"); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator strcpy (buffer[0], buffer[last_buf_line-1]); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator last_err_line = err_line; \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator last_buf_line = 1; \newline \protected_separator \protected_separator \protected_separator else { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator output_error (last_buf_line, last_err_line, "gcc"); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator last_err_line = 0; \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator last_buf_line = 0; \newline \protected_separator \protected_separator \protected_separator \newline \protected_separator \newline \newline \layout Scrap <<Function prototypes>>= \newline void discharge_buffer (int save_last); \newline \layout Standard To combine the scan of noweb error messages and xlc error messages is very simple. We just try each one for every input line: \layout Scrap <<AIX system using both noweb and xlc>>= \newline \newline \protected_separator last_buf_line = 0; \newline \protected_separator while (fgets(buffer[0], 200, stdin)) { \newline \protected_separator \protected_separator \protected_separator if (noweb_try(0)) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator output_error(1, 0, "noweb"); \newline \protected_separator \protected_separator \protected_separator else if (xlc_try(0)) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator output_error(1, err_line, "xlc"); \newline \protected_separator \newline \newline \layout Standard To combine the scan of noweb error messages and gcc error messages is simple if we realize that it is not possible to find a noweb error message in the middle of a gcc error message. So we just repeat the gcc procedure and test for noweb error messages in the beginning of the scan: \layout Scrap <<Solaris and Linux systems using both noweb and gcc>>= \newline \newline \protected_separator char \protected_separator \protected_separator \protected_separator *s, *t; \newline \protected_separator \newline \protected_separator last_buf_line = 0; \newline \protected_separator while (fgets(buffer[last_buf_line], 200, stdin)) { \newline \protected_separator \protected_separator \protected_separator /****** Skip lines until I find an error */ \newline \protected_separator \protected_separator \protected_separator if (last_buf_line == 0 && noweb_try(0)) { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator output_error(1, 0, "noweb"); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator continue; \newline \protected_separator \protected_separator \protected_separator \newline \protected_separator \protected_separator \protected_separator s = strpbrk(buffer[last_buf_line], " :"); \newline \protected_separator \protected_separator \protected_separator if (s == NULL || *s == ’ ’) \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator continue; /* No gcc error found here */ \newline \protected_separator \protected_separator \protected_separator do { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator <<gcc error message criteria is to find a "...:999:" or a "...: ">> \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator /****** OK It is an error, get line number */ \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator err_line = atoi(s+1); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator if (last_err_line == 0 || last_err_line == err_line) { \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator last_err_line = err_line; \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator continue; /* It’s either a header or a continuation, don’t output yet */ \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator \newline \protected_separator \protected_separator \protected_separator /****** Completed the scan of one error message, output it to LyX */ \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator discharge_buffer(1); \newline \protected_separator \protected_separator \protected_separator \protected_separator \protected_separator break; \newline \protected_separator \protected_separator \protected_separator while (fgets(buffer[last_buf_line], 200, stdin)); \newline \protected_separator \newline \protected_separator \protected_separator /****** EOF completes the scan of whatever was being scanned */ \newline \protected_separator discharge_buffer(0); \newline \newline \layout Section Wrapping the code into a file \layout Scrap <<listerrors.c>>= \newline #include <stdio.h> \newline #include <strings.h> \protected_separator \protected_separator \protected_separator \newline \protected_separator \newline <<Global variables>> \newline <<Function prototypes>> \newline <<Function bodies>> \newline \layout Standard To build this program, we want to add the \begin_inset Quotes eld \end_inset \begin_inset Quotes erd \end_inset option in the tangle command to force gdb to load the file \family typewriter Literate.nw \family default instead of \family typewriter listerrors.c \family default In accordance with this, we pass the \begin_inset Quotes eld \end_inset \begin_inset Quotes erd \end_inset option to gcc. \layout Scrap <<build-script>>= \newline #!/usr/local/bin/bash \newline notangle -L -Rlisterrors.c Literate.nw > listerrors.c \newline gcc -g -o listerrors listerrors.c \newline \layout Standard This project can be tangled and compiled from LyX if you set \family typewriter \backslash build_command \family default to call a generic script that always extracts a scrap named \family typewriter build-script \family default and executes it. Here is a example of such generic script: \layout LyX-Code #!/bin/sh \newline notangle -Rbuild-script $1 | sh \the_end

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