HP UX Web Development Tools specification

Example 53 Null pointer dereference check

A null pointer may result from null assignment or from a call to the APIs that may return a null value. If a pointer that is not guarded when it is dereferenced, unexpected runtime results may occur. For example, see the following program fragment:

#include <stdio.h>

int process (char* filename)

{

FILE* f;

int count = 0; if (filename)

{

if (f = fopen(filename, "r"))

{

while (fgetc(f) != EOF) count ++;

}

//f can be null at this point fclose (f);

return count;

}

return -1;

}

In such cases, cadvise generates the following warning:

"null.c", line 22, procedure process: warning #20200-D:

Potential null pointer dereference through f is detected (null definition:/home/sandyam/demo/null.c, line 16)

8.2 Detecting generic programming errors 47

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HP UX Web Development Tools Example 53 Null pointer dereference check, Such cases, cadvise generates the following warning

Contents

HP Code Advisor C.02.20 User Guide Page Contents Contents Related information Document conventions and symbolsAbout this document Intended audience Cadvise-help@lists.hp.com HP encourages your comments Cadvise user interface FeaturesCadvise user interface Features Introduction $ cadvise cc -c hello.c Advanced static code analysis $ cadvise -pdb ./mypdb +wlint aCC hello.cpp Supported compilers Getting started Using CadviseSteps in using cadvise Supported platforms Installing Cadvise Invoking Cadvise Integrating Cadvise with the makefiles and build process Using Cadvise as a wrapper around Compiler or LinkerFor information on PDB, see Using the Program Database PDB See the following makefile content Example 2 Sample wrapper script Enabling different categories of diagnostic messagesGenerating code complexity metrics Objfile.metrics Example 3 Generating code complexity metrics Generating code complexity metrics $ cat /tmp/example.c Example 4 Code complexity metrics +wcodeguide=rules-library Example 5 Writing a rule to enforce naming convention Source structure in the rules library Using the Program Database PDB Disabling locks in PDB operations PDB options tableSpecifying the PDB location Deleting PDB Example 9 Creating a PDB snapshot Creating a PDB snapshot at a specified locationDisplaying PDB version Example 8 Removing object file information from the PDB Cross-file analysis options Using cross-file analysisUsage Crossfile=auto Example 15 Specifying the location of object files Enabling warnings selectively Configuring diagnostic messagesDiagnostic configuration options table Suppressing warnings selectively Managing warnings in a source file Interpreting selective warnings as errorsDisabling warnings in a macro Cadvise report report-options logfile Generating reportsReport generation options table Cadvise report report-options -pdb pdbdir $cadvise report -summary -pdb testpdb -noheader Generating summary reportsGenerating file summary report Generating detailed report $ cadvise report -pdb testpdb -all To save reports, run the following commandGenerating Html report Example 23 Generating detailed report Example 24 Generating an XML report Printing diagnostics with specific diagnostic numbersFollowing example shows the command to generate XML report Generating XML report Example 26 Generating reports based on severity Suppressing diagnostics for specific filesGenerating reports based on severity $ cadvise report -pdb testpdb -diag $ cadvise report -pdb test.pdb -summary -include inflate.c Reporting diagnostics from specific filesReporting program complexity metrics $ cadvise report -pdb test.pdb -summary -exclude inflate.c $ cadvise report -pdb gzip.pdb +metrics -include inflate.c Generating report for a moduleExample 29 Reporting program complexity metrics $ cadvise report -pdb test.pdb -summary -module test1 Modifying the default severity level of a diagnosticSuppressing report header Generating PDB comparison report $ cadvise report -pdb tmp.pdb -basepdb tmp1.pdb -all Example 34 Generating detailed diff report with the header $ cadvise report -pdb tmp.pdb -basepdb tmp1.pdb -diag Example 35 Generating diff report for any particular warning $ cadvise -pdb pdb1 cc one.c two.c $ cadvise report -pdb tmp.pdb -basepdb tmp1.pdb -severity $ cadvise report -pdb new.pdb -basepdb old.pdb -all Report options file Example 41 Report options file Example 42 Generating a report using -migration optionGenerate report for migration related warnings Generating consolidated report from multiple PDBs $ cadvise report -pdb 1.pdb2.pdb3.pdb4.pdb -all Recommended process for analyzing the diagnostic messagesGenerating PDB diffs with multiple PDBs Report options interoperability $ cadvise report -pdb test.pdb -summary -include a.cb.c Example 44 Reporting options interoperability$ cadvise report -pdb test.pdb -diag 2549 -exclude b.c Example 45 Ignoring the -includeoption Example 47 Displaying the list of cadvise options Example 48 Using -noabortMiscellaneous driver options Help-h-H Following example shows the usage of -nobuildoption Example 49 Using -nobuild optionFollowing command creates the file cadvdir/foo.cad Example 51 Using -tee option Line generates the following messages Example 52 Using +opts filename option Detecting generic programming errors Categories of diagnostics with examplesCategories of diagnostics table Categories of diagnostics with examples Such cases, cadvise generates the following warning Example 53 Null pointer dereference check Such cases, cadvise generates the following warnings Example 54 Potential memory leak check Example 56 Out of scope access Example 55 Out of bound access Example 58 Allocator/deallocator mismatch Such cases, cadvise generates the following errorExample 57 Use of pointer after free Example 59 Signed bit field of length Detecting 32-bit to 64-bit migraton issuesDetecting endianness migration issues Example 60 Detecting 32-bit to 64-bit migraton issues Consider the following code fragment Detecting potential security vulnerabilitiesExample 61 Detecting endian dependent code fragments This case, cadvise generates the following error Detecting multi-threaded programming issues Detecting potential performance improvement opportunities Example 63 Detecting multi-threaded programming issuesRunning cadvise generates the following error Detecting potential performance improvement opportunities Fixing the warnings by source change AC++ standard conformance and compatibility changes Incompatibilities on PA-RISC based systems Index Symbols

HP UX Web Development Tools manual Example 53 Null pointer dereference check

Models: UX Web Development Tools

Example 53 Null pointer dereference check

In such cases, cadvise generates the following warning: