I found the following softwares that support UML code generation for C programming language:
As you know, Eclipse is an IDE that mainly for Java programming language. Eclipse has a capability to support features from its plug-in. One of them is UML generator. Eclipse UML generator supports Java and C programming languages. It can either generate or reverse. For this context, this plug-in has C code generator called UML2C. It converts class and state diagrams.
2. Enterprise Architect
Enterprise Architect is a modeling software. This software can be treated as an IDE for modeling because it has complex features. Enterprise Architect supports C code generation from UML models. It supports not only class diagram but also state, sequence, and activity diagrams. This feature guide is available on this page.
Astah is also a modelling software. It has some different products. Astah can generate C source code from UML class models via a plug-in called UML2c. This plug-in just only supports class diagram.
Note that, all of softwares above are not free software, except Eclipse. Astah can be purchased free for student only. I recommend to check the pricing page.
I don't know either if a modeling software can generate source code from ERDs. ERD is a model that draws relationship between data and basically for database. If I am not mistaken, you want to generate SQL from ERDs.