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Bug in C51 run-time library: sprintf

Andreas Hornsteiner

Hello,

I think I have found a bug in the sprintf function of the C51 run-time library:

If I call sprintf to substitute an integer ("%d", "%u" or "%i") from a one byte variable sprintf will write garbage into the array.

Here a simple example:

unsigned char xdata testArray[5] = ""; // testArray = {0x00, 0x00, 0x00, 0x00, 0x00}

unsigned char xdata oneByteVariable = 1;

sprintf(testArray, "%d", oneByteVariable); // testArray = {0x32, 0x35, 0x36, 0x00, 0x00} ASCII: "256"

If I use instead of a one byte a two byte variable, sprintf will work correctly:

unsigned int xdata twoByteVariable = 1;
sprintf(testArray, "%d", twoByteVariable); // testArray = {0x31, 0x00, 0x00, 0x00, 0x00} ASCII: "1"

I am using a silicon labs 8051 with the latest C51 development tools (version 9.55).

Can someone confirm this bug?

Best Regards,
Andreas Hornsteiner

Parents
  • 0 in reply to HansBernhard Broeker

    Yes of course I intended to write scanf - I actually misread the original question to mean scanf and not printf. That's why I later mentioned printf as a side note.

    For the standard integer promotion, it's enforced by most compilers since it's a requirement of the language standard, while C51 gives the user an option to go with compliance or with efficiency/size - all because the 8051 is badly suited for doing 16-bit arithmetic. Most other 8-bit processors have a better instruction set and/or register set for working on data larger than 8 bits.

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  • 0 in reply to HansBernhard Broeker

    Yes of course I intended to write scanf - I actually misread the original question to mean scanf and not printf. That's why I later mentioned printf as a side note.

    For the standard integer promotion, it's enforced by most compilers since it's a requirement of the language standard, while C51 gives the user an option to go with compliance or with efficiency/size - all because the 8051 is badly suited for doing 16-bit arithmetic. Most other 8-bit processors have a better instruction set and/or register set for working on data larger than 8 bits.

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