Christof points out problems with atoi() and line endings -- I ran into similar problems some time ago and resorted to sscanf()-ing what I read from the file to format it it 'properly' in memory before doing the conversion.
brad
On Mon, Aug 15, 2022 at 3:39 AM Christof Ressi info@christofressi.com wrote:
Edwin has already pointed out the immediate error in your code.
However, there are a lot more problems. First some general issues:
- you need to free the line buffer before returning from the function,
otherwise there will be a memory leak.
- AFAICT, the string buffer passed to atoi() is not NULL-terminated.
atoi() stops after encountering a non-numeric character, so depending on the data that happens to be on stack, this might appear to work - but it can also easily lead to wrong results!
- The default line ending on Windows is CRLF (13 + 10) instead of just LF
(10), so depending on how the file was created, your code might not work correctly.
Now some remarks about the actual code. IIUC, what you try to do is read the content of the text file into a two-dimensional array. Your approach seems to be the following: loop backwards character by character and manually assemble the decimal numbers from individual digits. First off, in this case there is need to call atoi() in the first place because you already know the value of the digit. On the other hand, this is completely unnecessary because atoi() can parse *numbers *- not only digits! For example, atoi("1024") will output an integer 1024.
Unfortunately, atoi() has a few problems: it does not handle errors and it does not give you the position after the number, so you need to manually search for whitespace/newlines. https://cplusplus.com/reference/cstdlib/strtol/ https://urldefense.proofpoint.com/v2/url?u=https-3A__cplusplus.com_reference_cstdlib_strtol_&d=DwMFaQ&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=TUSlFmJ_9hRhpnUmWLtwdEo8SXGhxgz2NDS43-6hnKg&m=5HPO3yP5cO7EAoTCLdg8pt_pFjHj1F_sb9fmPj7RONcdAsUqm3_qp-YU6QFsBjhO&s=aojlAfmm0qrla86hNuWi_ywdPlUiiQh4BXpvgdwQljA&e= solves both issues.
The most idiomatic way for reading a sequence of numbers from a textfile in C would be https://cplusplus.com/reference/cstdio/sscanf/ https://urldefense.proofpoint.com/v2/url?u=https-3A__cplusplus.com_reference_cstdio_sscanf_&d=DwMFaQ&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=TUSlFmJ_9hRhpnUmWLtwdEo8SXGhxgz2NDS43-6hnKg&m=5HPO3yP5cO7EAoTCLdg8pt_pFjHj1F_sb9fmPj7RONcdAsUqm3_qp-YU6QFsBjhO&s=NQmHaCycNfkE6pc2Lw_VRoGaSYkZeYhDtqKZr8ih0jM&e=. Your code could be rewritten as follows: int readbarfile(int a[][8], FILE *f) { int row = 0; char * line = NULL; size_t len = 0; while (getline(&line, &len, f) != -1) { int col, value, nread, pos = 0; for (col = 0; col < 4; col++) { // We expect 1 converted element. // (%n does not count, it only tells the current stream position.) if (sscanf(line + pos, "%d%n", &value, &nread) == 1) { a[row][col] = value; pos += nread; } else { // handle conversion error } } row++; } free(line); return row; }
Since you are dealing with a fixed column size, this could be simplified further: int readbarfile(int a[][8], FILE *f) { int row = 0, col; char * line = NULL; size_t len = 0; while (getline(&line, &len, f) != -1) { // We expect 4 integer items. Actually, we can directly read into the output array // because the data type (int) matches the %d specifier. if (sscanf(line, "%d%d%d%d", &a[row][0], &a[row][1], &a[row][2], &a[row][3]) != 4) { // handle error } row++; } free(line); return row; }
Christof On 15.08.2022 08:29, Jaime Oliver wrote:
Hi Chris, Brad, All,
I managed to trace the error to the function below. It reads a text file and copies its contents to a matrix. The file it's reading is always made of lines with the same number of elements like this below:
0 4 4 8 32 1 4 4 8 32 2 4 4 8 32 ...
The specific error I'm getting right now is that it is reading that number 32 as 29. Again, this same code works fine in all other OSs I've tried.
I'm assuming the issue is in the pow() function and all the typecasting (int), (double) as Chris suggested?
As for compilation, I am using the latest pd_lib_builder as the makefile.
Thanks for your help!
best,
Jaime
code:
int readbarfile(int a[][8], FILE *f) { int i, ii, j, jj, strsize, temp; char * line = NULL; size_t len = 0; ssize_t read; char ss[10]; temp=j=0; ii=0; while ((read = getline(&line, &len, f)) != -1) { jj = 4; strsize = (int) read; for (i=strsize-1; i>=0; i--){ if ( line[i] == (int) 32 || line[i] == (int) 10) { //space or newline if(i != (strsize-1)) { a[ii][jj] = temp; jj--; } j=0; temp=0; } else { ss[0] = line[i]; temp += atoi(ss)*( (int) pow((double)10, (double)j) ); j++; } } ii++; } return (ii); }
On Fri, Aug 12, 2022 at 1:57 PM Chris Clepper cgclepper@gmail.com wrote:
That issue only relates to data corruption in the case of major failures like power loss and kernel panics. In most of those situations some data loss is not only expected but also the least of your concerns.
As for the original topic, the first thing to check is the usual problems moving between architectures like endianess, definition of data structures (is long really 32 bits, double 64 bits, etc), memory alignment and compiler settings. Does the code work with all of the optimizations turned off?
On Fri, Aug 12, 2022 at 5:58 AM Bastiaan van den Berg buzz@spacedout.nl wrote:
Did you read that M1's storage has so much cache + lies to the OS about cache commitments, leading to data corruption sometimes? https://twitter.com/marcan42/status/1494213855387734019 https://urldefense.proofpoint.com/v2/url?u=https-3A__twitter.com_marcan42_status_1494213855387734019&d=DwMFaQ&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=TUSlFmJ_9hRhpnUmWLtwdEo8SXGhxgz2NDS43-6hnKg&m=5HPO3yP5cO7EAoTCLdg8pt_pFjHj1F_sb9fmPj7RONcdAsUqm3_qp-YU6QFsBjhO&s=oiKhcMBiqQPZXOuU59byzkz6mJov0w-_kEaq00lsSXg&e=
On Fri, Aug 12, 2022 at 6:14 AM Jaime Oliver jaime.oliver2@gmail.com wrote:
Dear all,
I have a c external that compiles and runs fine on windows, Linux, and Mac Intel systems, but while the exact same code compiles ok on a Mac M1 system, it runs with errors.
I am trying to figure out the bug, but wonder if anyone has come across something like this? The external itself is not particularly complex. It writes and reads text files, does basic arithmetic, and uses arrays of various sizes.
Does anyone have any suggestions of where to look first?
Best,
Jaime _______________________________________________ Pd-list@lists.iem.at mailing list UNSUBSCRIBE and account-management -> https://lists.puredata.info/listinfo/pd-list https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.puredata.info_listinfo_pd-2Dlist&d=DwMFaQ&c=009klHSCxuh5AI1vNQzSO0KGjl4nbi2Q0M1QLJX9BeE&r=TUSlFmJ_9hRhpnUmWLtwdEo8SXGhxgz2NDS43-6hnKg&m=5HPO3yP5cO7EAoTCLdg8pt_pFjHj1F_sb9fmPj7RONcdAsUqm3_qp-YU6QFsBjhO&s=C9xTf51AkTfmar1-nEEfndNgNbpQJenqK5zX0_BfG50&e=
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