Implementations
Most C compilers now have support for at least some of the features new to C99. However, there has been less support from vendors such as Microsoft that have mainly focused on C++.
| Implementation | Level of support | Details |
|---|---|---|
| AMD x86 Open64 Compiler Suite | Mostly | Has C99 support equal to that of GCC. |
| cc65 | Partial | Full C89 and C99 support is not implemented, partly due to platform limitations (MOS Technology 6502). There is no support planned for some C99 types like _Complex and 64-bit integers (long long). |
| Ch | Partial | Supports major C99 features. |
| Clang | Mostly | C99 floating-point pragmas are the only unsupported feature. |
| cparser | Mostly | Supports most C99 features. |
| C++ Builder | Mostly |
|
| Digital Mars C/C++ Compiler | Partial | Lacks support for some features, such as tgmath.h and _Pragma. |
| GCC | Mostly | As of July 2011 in mainline GCC, 43 features have been completely implemented (12 suffer library issues), 1 feature is broken and 6 are missing. GCC's 4.6 and 4.7 releases also provides the same level of compliance. |
| IBM C for AIX, V6 and XL C/C++ V11.1 for AIX | Full | |
| IBM Rational logiscope | Full | Until Logiscope 6.3, only basic constructs of C99 were supported. C99 is officially supported in Logiscope 6.4 and later versions. |
| The Portland Group PGI C/C++ | Full | |
| Intel C++ compiler | Mostly | |
| Microsoft Visual C++ | No | As of Visual C++ 2010, there are no plans to support C99. The forthcoming Visual C++ 2011 will also lack C99 support. |
| Open Watcom | Partial | Implements the most-used parts of the standard. However, they are enabled only through an undocumented command-line switch. |
| Pelles C | Mostly | Supports most C99 features. |
| Portable C compiler | Partial | Working towards becoming C99-compliant. |
| Sun Studio | Full | |
| Tiny C Compiler | Partial | Does not support complex numbers, variable length arrays and for loop initial declarations. The developers state that "TCC is heading toward full ISOC99 compliance". |
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