Microsoft KB Archive/93401

= PRB: C2279: Braces Not Valid in Function Default Argument List =

Article ID: 93401

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 1.0 Professional Edition
 * Microsoft Visual C++ 1.5 Professional Edition
 * Microsoft Visual C++ 1.51
 * Microsoft Visual C++ 1.52 Professional Edition
 * Microsoft Visual C++ 1.0 Professional Edition
 * Microsoft Visual C++ 2.0 Professional Edition
 * Microsoft Visual C++ 2.1
 * Microsoft Visual C++ 4.0 Standard Edition
 * Microsoft Visual C++ 4.1 Subscription
 * Microsoft Visual C++ 4.2 Professional Edition
 * Microsoft Visual C++ 5.0 Standard Edition
 * Microsoft Visual C++ 6.0 Service Pack 5
 * Microsoft Visual C++ .NET 2002 Standard Edition

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This article was previously published under Q93401



SYMPTOMS
When Microsoft C/C++ compiles an application that specifies a structure in the default arguments for a function, the compilation fails with the following error messages:

error C2059: syntax error : '{'

error C2279: cannot use braces to initialize default arguments

If you are using Visual C++ .NET compiler, the following compiler errors will be generated instead of the above two compiler errors.

error C2143: syntax error : missing ')' before '{'

error C2059: syntax error : ')'



CAUSE
According to the C++ grammar, the default value for an argument must be an expression. An initializer list, such as that used to initialize a structure, is not an expression.



RESOLUTION
Define a constructor to perform the required initialization.



MORE INFORMATION
The first code example demonstrates the errors listed above. The second code example demonstrates the correct method to initialize the structure.

Code Sample 1
/* * Compile options needed: /c */

struct ag_type {  int a;   float b; };

void func(ag_type arg = {5, 7.0});

Code Sample 2
/* * Compile options needed: /c */

struct ag_type {  int a;   float b;   ag_type(int aa, float bb) : a(aa), b(bb) {} };

void func(ag_type arg = ag_type(5, 7.0));

Additional query words: 8.00 8.00c 9.00 9.10

Keywords: kbprb kbcpponly kbcompiler KB93401

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