access violation calling FindNextFileA

[blametroi]

I've been working on my API testing program and with the prior advice I've made pretty good progress, but now I get an access violation after some number of calls to FindNextFileA. It appears to be deterministic, if I change the file spec I am searching for, I can get a different number of looping calls to FindNextFileA before the failure.

I'm not a C++ programmer so I'm not sure how to approach this on my own.

Event log information and code attached. Failure occurs on the call:

    Result% = FindNextFile&(hFind&, ffd)

I've confirmed that the ffd structure is the correct length so there's no overwrite of memory that could be happening there. I've thrown in some debug prints and the find handle doesn't appear to get walked on either.

Ideas/advice?

Log Name:      Application
Source:        Application Error
Date:          12/28/2018 9:17:10 PM
Event ID:      1000
Task Category: (100)
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      yirgacheffe.blametroi.com
Description:
Faulting application name: winapitesting.exe, version: 0.0.0.0, time stamp: 0x5c26d8e5
Faulting module name: msvcrt.dll, version: 7.0.17134.1, time stamp: 0xc5dd3631
Exception code: 0xc0000005
Fault offset: 0x00088a7a
Faulting process id: 0x61f8
Faulting application start time: 0x01d49f1c9a214fb7
Faulting application path: E:\programming\qb\winapitesting.exe
Faulting module path: C:\WINDOWS\System32\msvcrt.dll
Report Id: d579a6ac-77a9-4b93-afce-1287162c2c56
Faulting package full name:
Faulting package-relative application ID:

Code: QB64: [Select]

1. ' windows api testing, build a set of
2. ' useful routines
3. ' starting code is lifted from the qb64.org wiki to
4. ' bootstrap the effort, then i'll add my own stuff.
5. '
6. ' txb 27 December 2018
7.  
8. OPTION _EXPLICIT
9.  
10. ' use a cmd console window instead of a screen
11. $CONSOLE:ONLY
12. _DEST _CONSOLE
13.  
14. ' *************************************
15. ' Windows API constants and types
16.  
17. CONST MAX_PATH = 260
18.  
19. ' FINDEX_INFO_LEVELS
20. CONST FindExInfoStandard = 0
21. CONST FindExInfoBasic = 1
22.  
23. ' FINDEX_SEARCH_OPS
24. CONST FindExSearchNameMatch = 0
25. CONST FindExSearchLimitToDirectories = 1
26. CONST FindExSearchLimitToDevices = 2
27.  
28. ' Error codes from Windows
29. CONST ERROR_FILE_NOT_FOUND = 2
30. CONST ERROR_NO_MORE_FILES = 18
31.  
32. ' WIN32_FIND_DATA
33. TYPE FindFileData
34.     FileAttributes AS LONG
35.     CreationTime AS STRING * 8 ' actually these are FileTimes, 64 bit nanoseconds from 1601
36.     LastAccessTime AS STRING * 8
37.     LastWriteTime AS STRING * 8
38.     FileSizeHigh AS LONG
39.     FileSizeLow AS LONG
40.     reserved0 AS LONG
41.     reserved1 AS LONG
42.     FileName AS STRING * MAX_PATH
43.     AlternateFileName AS STRING * 14 ' DOS 8.3 format name
44.     FileType AS LONG
45.     CreatorType AS LONG
46.     FinderFlags AS INTEGER
47. END TYPE
48.  
49. ' *************************************
50. ' Windows API functions, some originally from
51. ' qb64.org/wiki examples, others created for this
52. ' effort.
53.  
54. DECLARE LIBRARY 'Directory Information using KERNEL32 provided by Dav
55.     FUNCTION GetWindowsDirectory ALIAS GetWindowsDirectoryA (lpBuffer AS STRING, BYVAL nSize AS LONG)
56.     FUNCTION GetSystemDirectory ALIAS GetSystemDirectoryA (lpBuffer AS STRING, BYVAL nSize AS LONG)
57.     FUNCTION GetCurrentDirectory ALIAS GetCurrentDirectoryA (BYVAL nBufferLen AS LONG, lpBuffer AS STRING)
58.     FUNCTION GetTempPath ALIAS GetTempPathA (BYVAL nBufferLen AS LONG, lpBuffer AS STRING)
59.     FUNCTION GetModuleFileName ALIAS GetModuleFileNameA (BYVAL hModule AS LONG, lpFileName AS STRING, BYVAL nSize AS LONG)
60.     FUNCTION FindClose (hFindFile AS LONG)
61.     FUNCTION GetLastError& ()
62. END DECLARE
63.  
64. DECLARE CUSTOMTYPE LIBRARY
65.     ' Per FillippeHeitor at qb64.org, moved from 'declare library'
66.     ' to 'declare customtype library' to get around a C++
67.     ' compile error. Interestingly, the various functions in the
68.     ' above 'declare library' fail if put under 'customtype'.
69.     FUNCTION FindFirstFileEx& ALIAS FindFirstFileExA (lpFileName AS STRING, BYVAL fInfoLevelId AS LONG, lpFindFileData AS FindFileData, BYVAL fSearchOp AS LONG, BYVAL aNull AS LONG, BYVAL AdditionalFlags AS LONG)
70.     FUNCTION FindNextFile& ALIAS FindNextFileA (BYVAL handle AS LONG, lpFindFileData AS FindFileData)
71. END DECLARE
72.  
73. ' *************************************
74. ' Variables and more variables
75.  
76. DIM ResultLength&
77. DIM CurrentDirectory$, ModuleFileName$
78. DIM ffd AS FindFileData
79. DIM searchString AS STRING * MAX_PATH
80. DIM hFind&
81. DIM LastError&
82. DIM Result%
83.  
84. ' *************************************
85. ' Some process related information
86.  
87. ' SHOW CURRENT DIRECTORY
88. CurrentDirectory$ = SPACE$(MAX_PATH)
89. ResultLength& = GetCurrentDirectory(MAX_PATH, CurrentDirectory$)
90. IF ResultLength& THEN
91.     PRINT "CURRENT DIRECTORY: "; LEFT$(CurrentDirectory$, ResultLength&)
92. END IF
93.  
94. ' SHOW CURRENT PROGRAM
95. ModuleFileName$ = SPACE$(MAX_PATH)
96. ResultLength& = GetModuleFileName(0, ModuleFileName$, MAX_PATH)
97. IF ResultLength& THEN
98.     PRINT "CURRENTLY EXECUTING PROGRAM: "; LEFT$(ModuleFileName$, ResultLength&)
99. END IF
100.  
101. ' *************************************
102. ' look for a likely non-existing file to demonstrate
103. ' error handling
104. '***to be provided***
105.  
106. ' *************************************
107. ' list all the *.bas files in the directory
108. PRINT
109. searchString = "*.*" + CHR$(0)
110. PRINT "seeking files matching "; searchString
111. hFind& = FindFirstFileEx&(searchString, FindExInfoStandard&, ffd, 0&, FindExSearchNameMatch, 0&)
112. IF hFind& < 0 THEN
113.     LastError& = GetLastError&
114.     PRINT "find first failed for "; searchString
115.     PRINT LastError&
116.     DIM a$
117.     INPUT a$
118.     SYSTEM 0
119. END IF
120. PRINT "found some files:"
121. PRINT LEN(ffd)
122. DO
123.     PRINT LEFT$(ffd.FileName$, Strlen(ffd.FileName$, MAX_PATH))
124.     'PRINT "found ", ffd.FileName$
125.     'PRINT Strlen(ffd.FileName$, MAX_PATH%)
126.     PRINT hFind&
127.     Result% = FindNextFile&(hFind&, ffd)
128.     PRINT Result%
129. LOOP WHILE Result%
130. DIM george$
131. INPUT george$
132. Result% = FindClose(hFind&)
133. PRINT Result%
134.  
135. DIM fred$
136. INPUT fred$
137. ' and done
138. SYSTEM 0 ' instead of END
139.  
140. ' *************************************
141. ' Return length of a null terminated (asciiz) string
142. '
143. ' this is bugged, it isn't going to handle zero
144. ' length strings correctly
145. ' nor max length strings
146. FUNCTION Strlen% (s AS STRING * 1, maxlen AS INTEGER)
147.     DIM i AS INTEGER
148.     i = 1
149.     WHILE i < maxlen AND ASC(MID$(s, i)) <> 0
150.         i = i + 1
151.     WEND
152.     Strlen% = i - 1
153. END FUNCTION
154.  

[TempodiBasic]

Hi
running in windows 10 64bit on intel i3  4GigaRam 500HDD and compiling with QB64 32bit version 1.2 Dev e490b1a

I got as results 5 printed informations and then an "out of memory" critical error with only OK button to accept the crashing of instance runned.
In the folder in which the application runs there are 13 files.

[blametroi]

More ram here but also Windows 10 (pro) 64-bit. I've got the latest dev build downloaded, git 6fe5c48. For me the app just disappears and the event log is updated. I'm trying with the release build to see if I can get any different information.

[TempodiBasic]

Changing your code, putting out your function Strlen%,

Code: QB64: [Select]

1.  
2. PRINT LEFT$(ffd.FileName$, Strlen(ffd.FileName$, MAX_PATH))

to

Code: QB64: [Select]

1. PRINT LEFT$(ffd.FileName$, INSTR(ffd.FileName$, CHR(0)) -1)
2.  
3.  

  I got only an application  that  crashes suddenly.